It's easy to do but it normally messes up the paint pretty badly. You would braze or weld them. These can be brazed with a propane torch. There are frame supply shops like ceeway in england, but these are just little bits of rod tapped for 5mm bolts and attached to the frame. Not worth writting away for. You can also work out ways of tying on frnders with zip ties, using brake or drain holes. ANd racks can be attached to axles, hardware held by the axels, or clips to the tubing.