Halo 3 walkthrough and other

now probz most of you now that halo 3 has a theatre that lets u make movies and stuff like that, and i wanna make a walkthrough for the missions and even make a few funny videos and i'll put them on youtube but again probz most of you know that on movie maker if most of you have it you cant put movies on it that you uploaded form your phone to your computer, so if i put the halo 3 vids i make onto my phone i wont be able to edit them and put them on youtube so how the hell am i gunna get them from ym xbox 360 to my comp without using my phone, know i now that most of you have done this and put them on youtube, so could you plz help fid a way to do that, and if i have to download a program so be it, but plz only tell me something tha is free and i do not have to pay for, abnd it wud help if everyone that saw this posted a comment =] thankyou