Pick out a patch, place it in the place you'd like to sew it and pin it in place.
Thread a needle and start from the back of the material your attaching the patch to.
Make sure your patch is lying flat. And make sure you're pulling your stitches tight.
When you've sewed all the way around the patch poke your thread through the back of the patch, and you can tie a knot and cut the excess thread or weave the excess thread through the existing stitches