New to viz.com/shonenjump

So, I'm new to viz.com/shonenjump and i can't find a way to buy cards, but I've seen ppl talking about prono codes and stuff. I saw some cards I'd like to get, but I can't buy them. I also signed up but it juat asked me for personal info and when i signed up it made no difference, although i didn't check my email. Help me please