Help❓ How to add additional class boxes.

Hi, guys. Basically, what the title says I would like to add more class boxes in the client. Sadly, i do not know what to edit in the client so I need some help on how to do this . (not classes themselves I mean class boxes ._.)

I could help you with it.
Do you want steps or should I do it for you?

dude you suck and you leach xD stahp asking slender
gimmeh tabs