ok, its really easy....
i never upholstered a car before, but i decided to try it, this was about 10 years ago now.
first note, my interior somebody had attempted a DYI upholstery on. What i had was seats in really bad shape, and as it turned out the front seats had the original material underneath the crappy re-covers.
first thing you need; a REALLY good hog ring tool. Do not mess around get the top of the line tool you can find, the junky little one that comes with kits will break apart in no time. next, a camera, take lots of photos. Do not throw anything out until the project is 100% complete. the original covers will be your guide and you will need to grab parts off them.
materials you will need, Burlap, Muslin cloth, piano wire.
you may also need new springs.
first you start taking the seats apart and breaking them down, take pictures, put the hardware in baggies.
next you start poping the original hog rings, you need a good wide plyer, you grab the ring and twist it, that opens up the jaws and you can slide them out.
work slow, take photos and notes as needed.
break it down in stages. top cover, muslan foam layer, then the burlap and wires. get down to the metal frame and inspect it.
you will always find cracks, broken springs, broken welds. you will need to make the repairs, before rebuild.
I recommend rust converter or sand blasting the frames, then repaint with rustolem or something like it.
paint the frames in the primary color of the material your using for the seat covers. green covers, paint them green, red/red, black/black etc...
once the frames are good to go. inspect the burlap layer.
the purpose of the burlap layer is to contain the foam layer so it doesn't rip through the bottom of the seat it also adds to a the base over the springs.
the burlap is a cut shaped piece and it has piano wire equality spread in one direction in it.
easy to recreate. cut out a new shaped piece as needed, then fold the material like an accordion and weave new piano wire through it then lay it flat and it should match the original. i think it took me 4 hours to recreate all the burlap pieces needed for the front and back, i got the wire at a local hobby shop.
the wire is kind of thin.
you attach the burlap to the springs just like original with hog rings. look at your photos you took.
next is the foam layer you need some spray adhesive that is good on foam, i hit micheals arts and craft for it.
inspect the reproduction foam for rips, if it is ripped you can glue it together however i would return it for a good one.
look at the original foam. it has muslin cloth glued to the sides , copy the pattern to and transfer to new material , glue to the new foam, and re-hog ring just like original to the frame.
you will also notice some jutting you might be able to reuse it or you can replace it with carpet underlayment.
glue it to the foam on the sides as original.
ah the seat cover. inspect the original material, REMEMBER never throw anything out EVER!
you will need to cut the original seat badge out, we get to this in a minute.
but inside the original seat material you will find thick piano wire for all the folds in pockets these pockets exist on the reproduction seat covers.
they do 2 things, in some areas they are anchor points for the hod rings and in other areas that force the seat to conform and look correct over the foam.
so transfer all the original piano wire to the new seat cover and try to match placement as best you can. the repop stuff is hit or miss somebody always forgets to install one of those pockets.
now the badges. i ended up installing badges 5 years apart from when i did my seats. this was because i never had the original badges in the first place and a friend found a pair he had cut from an old seat. the thing is they are easy to install with a trick.
when you cut them from the original seat material you will notice they have a backing plate. the arms that hold the badge to the plate were melted at high temperature, take a shear cutter and cut a line from the bottom of the plate to the melted arm do the same for the other side. then bend the plate(tin) to open up the cut so you can slide the plate up that will release the badge from the seat material, clean the badge up, repaint if needed.
open a small hole in the new seat cover right where the arms are on the badges just like the original covers. you can use a knife or you can use a solder iron on low heat to melt the material a little, melting is better but dangerous i opened up the stitching a little on mine in that area then restitched after.
so now you slide the plate back under the melted arms of the badge and use a plier and close up the cuts you made on the tin plate.
then you take your solder iron and solder the plate with some silver solder to hold the cut together.
phew your ready to install the covers.
now the trick with the hog rings is it holds the material to the seat frame, but also you can fold and stretch the covers and hold them how you need just placing the hog rings in a different spot or adding more then one. if you screw up or don't like how the material stretched, take your plier twist the hog ring and take it off and try again.
it really isn't hard just time consuming.
it took me 2 weekends (4 days) to complete my front and rear seat. and then later i went back pulled my front covers off and installed the badges and that took me 4 hours since i figured it out the first time.
now it is nicer to do this in the summer because you can layout the covers in the sun and let them get soft. however you could lay throw them in the dryer on low for 15 minutes or set them on a heated blanket or super heat your garage with a propaine heater to soften them up.
well like i said i NEVER did it before and people swear a pro did my car but i have some photos proving i did it. if you screw up you can always start over.