You can register users manually, or with a premade query or script. Both of these can be found on the forum. Search bar is your friend.
PvP Rankings (assuming you want it on a website) is going to require a script. Again, it can be found on the forum using the search bar.
To use the scripts you are going to need Apache or IIS installed and configured correctly. There are guides on this all over the place. Apache is pretty straight forward depending on what your intended use is (Public or Private). After that you just drag the scripts that you have edited with your information into the htdocs/publichtml/www (folder that your web server is serving files from) and you should then be able to view them from a browser.