How do people create fan made anime fights?

[daniel2099]

I'm using these videos as an example. 

https://www.youtube.com/watch?v=D-PnRiH7fPg https://www.youtube.com/watch?v=XzGVE7fZlDg

I'm asking because I wanted to make a similar one but better. Is there a website that anyone can point me in the right direction where I can find anime characters for editing but without a background so that I can use in editing or are is that not possible and I have to edit this from scratch using a program like sony vegas or adobe premier? I'm asking because no one really tells me how this is done.