as stated earlier, amvapp is a collection of programs that aid you in the amv making process
more specifically it allows you to rip footage from dvds, transcode the vob files (and index them), clean up the footage and encode it.
this makes the footage from dvds usable in most editing programs (also includes a few audio tools too IIRC)
to use it...read the guide that you were linked to 3 times.
you will probably need a new editing program to pull off effects that aren't avaliable in WMM (unless there are a lot of 3rd party plugins) but you would probably be better off making a few in WMM to get used to making amvs
after that (or right now if you are so inclined) you can check out a list of free/open source software
located here