In general, the rules are with "I, you, we, they" use "do", with "he, she, it" use "does". I do my homework. You do your homework. They do their homework. We do our homework. She does her homework. He does his homework. It does its homework. The same works with "do not" and "does not" I do not do my homework. We do not do my homework. They do not do their homework. You do not do your homework. He does not do his homework. She does not do his homework. It does not do its homework.

I do my homework --right I does my homework---wrong He does his homework---right He do his homework----wrong I don't do my homework--right I don't does my homework---wrong he doesn't do his homework ---right he doesn't does his homework---wrong Always remember, "does“ follows with he, she, it; while "do" is after I, they, you;