It's actually (mostly) pretty simple once you get the basic idea. I can remember playing number and letter games in primary school, not knowing that this is what it was. It stuck with me, I've always had a thing for maths and I guess that converting letters to numbers is no different. If you are looking for a place to start, check out the gematrinator - it is super helpful.  http://www.gematrinator.com/calculator/index.php