The most basic thing you need is a good compression program to open ZIP and RAR folders and files. 7-Zip, Winzip, and WinRAR are the major players in this arena. Whichever one works for you is fine, as long as it works. Almost all of things you want to download will be in a ZIP or RAR file format. You can download these programs and decide which one (or ones) you like by clicking the Download tab at cnet.com.
I really enjoy this part of MMD-ing! What never ceases to amaze me is the sheer amount of pure creativity people up load. Daily, someone has a new dance, skit or meme available. MMoDlers (my terminology) create and upload a diversity of new models. You can also subscribe to and learn from them. Making friends with an MMoDler could open the door to custom model work. 2b1af7f3a8