Welcome to the board! First and foremost, take it to the vet and have it checked out for all the problems that afflict strays. FLV, FIP etc...It probably has black gunk it it's ears- ear mites and the vet can help to clean out the ears without a problem and give you medicine for them. Also it probably has fleas and worms so a vet check is the first thing to really do.
Other than that, work slowly and gently with it, give it lots of love and food and fresh water, keep a clean litterbox and play with it during the day so it can get used to you. But accept my thanks for taking another stray off the street! Good job!
Welcome to the site Parker! I add my thanks to Hissy's for taking in that baby off the street. You have most likely added years on to his/her life, and definitely added quality of life that the little angel wouldn't have had without you. Your rewards will be great - the ones we take out of bad situations, whether off the street, from a shelter, or even worse, always seem to know that you "saved" him/her. They develop a very, very special bond with their person.
If you have any more questions about anything with your new baby, just ask. People here are very nice, and very knowledgable about kitties. Certainly, never feel like any question you have is too elementary. We all had our first cats at one point, and we learn from our own and others' experience.