Felldonkey, first thing to think of is rear stay rear frame spacing, gap between rear dropouts. These ideally have to match your hub width on your back wheel. If your back wheel fits your away. If it don't then you can cold set it with a plank of wood. Basically and this is a trick I learnt at Raleigh. Lay the frame on it's side, put the 2x2 bit of wood either inside or outside the seat tube the if it's long enough either gently press down or pull up against the dropout. This will cold set the frame. Takes a steady hand and eye but it's fairly easy to do. Once you have the wheels in your frame your away. You can go from there. Brake caliper length may be an issue. If you need a longer drop to suit your rims , often this is a problem on old steel frames. Just get tektro calipers that suit 80mm drop.
Get your front and rear mech fitted and and that's about it.
Like I say , check your gap, fit your wheel and get a cassette on.
The front mech can be set with a ten pence piece, that's what I use. And then get your cables on and then adjust your gears.
Good luck
What frame is it