..and stamina? I've tried using the one found on UESPWiki, but it's BS and doesn't work.

player.modav health xxx

player.modav stamina xxx

player.modav magicka xxx

just replace xxx with desired number

What exactly are you typing in? No, seriously, just in case you're typing it wrong. Definitely make sure you start with player., otherwise it probably won't work (e.g. player.additem, not just additem).

The command should be 'player.setav health xxxx', where xxxx is the amount of health you want. What were you putting in that wasn't working?

EDIT: Actually, what's the difference between 'modav' and 'setav'?