ooohh ok. I'll give you a quick run through.
First you need vids, and I guess you have that covered.
Next you need some sort of video editing software. There are plenty out there. I went with Sonic Foundry's Vegas Video 3.0. Now I opted the $300+ software from online, and went the kazaa way. There is a Vegas Video 4.0 out but I can't find it, and so far 3.0 is fine with me.
If you need help working the crack for Vegas Video just ask, I'll see if I remember how to do it. It involves a little more than the usual replacement or input of serial #.
After installing it is where all the difficulty comes. When you create a new project you basically can throw any audio or video in there. From that point it is where if you mess around you learn things. I still havent learnt to use every tool but 6 vids later (first five were GT3 vids) I have gotten better at this. If there are any individual things you need to know, like how to work with the effects and such, just ask.