get some polyester thread the same color as your wig, some scissors, a regular sewing needle, the clips, and your wig and get ready (tutorial pictures from arda.com)
put about three in at the front hairline of your wig, one center, and two more about and inch or two away from it. place about ¼ inch between the hairline and where the top of the clip is. that way you aren’t able to see the clip or the hair it is attached to when you sew it in
NOW MAKE SURE THE CLIPS TEETH ARE FACING INWARD! they must be on top and facing the inside of the wig for this to work
now sew these things in. do one hole at a time, and be sure to move the wig hair out of the way on the other side so you don’t get it all tangled up. loop it through the hole about 4 times, then tie the thread off. when cutting them off, make sure you don’t cut the wig hair. sew all the holes to the cap and BAM. it’s ready to put on
put on your wig cap and wig as normal, just this time pull the wig forward slightly so that you can hook the clips to the hair under the cap (make sure they get the hair, not just the cap).