How do you do black weaves?

There are several methods to apply weaves/hair extensions, but since your question is in Beauty, Hair, & Sewing, I'll explain the sew-in method:

The hair is braided and with a needle & thread, the weft of hair is literally sewed onto the head via cornrow/braid. Sounds confusing but it really isn't. Depending on how sensitive you are and how tight your braids are, this can hurt or feel like nothing. If this is your first time having your hair braided, the braids may seem a little tight, which causes pressure. If this happens to you, tell your stylist. It's better to have the problem fixed immediately rather than having to take it all out. No pain whatsoever should come from the needle due to it not coming near nor puncturing skin.