HELP I HAVE TO RUN 3 MILES!!

Okay so I have to be able to run 3 Miles without stopping by May and I'm not fit not athletic at all! I need help! If anyone here is a runner and has run 3 Miles or more without stopping please help me and give me tips like how to breath or pace yourself etc. I've started running today actually and ran around my block and when I got out of breath I started walking  until I could start running again, but I didn't stop loving. This is so sad that I can do this,