It depends on your level of competency with working on a computer.
No Competence (aka: “I had problems hooking up the controller.”)
Hmmm, probably shouldn’t bother, but you do have contributions to the Stack Exchange network, so I don’t think you’re at this level.
Minimal (aka: “I plug it in and press buttons. I can use Google.”)
Look for the software that came with the gamepad. They are usually setup to simply work with their own products, and has a lot less hassles to deal with. Start with the manufacturer’s website, then try the model numbers on compatible 3rd party software.
Intermediate (aka: “I know how to code.”)
There are many pieces of software out there that allow you to configure exactly what anything attached to your computer can do. At the easiest level would be scripts such as AutoHotKey or AutoIt that captures the input and lets you assign whatever you want to it.
I use AutoHotKey myself and I assign keyboard buttons to the controller. I also setup a modifier key on the controller to turn on rapid fire. I sometimes even put in entire combos into one button (e.g. fireball) so I press a single button to do a move. It’s borderline cheating so don't do that if that bothers you.
Some reading required, and probably more asking for help on their respective forums to get things to work.
At more complex levels you write your own hooks and run them, but if you know how to do that, you wouldn’t be asking.