Could someone help me PLEASE?

ok so im trying to đăng tải a video on to Youtube and i made it bởi using Windows movie maker, i published it and used the avi format but when i tried uploading it , the file was too big and was taking forever even though it is only 2 mins long. im very fustraited, i want to know how to make it smaller if possible, if anyone could help it would be great. thanks