I recommend OpenTabletDriver now. I made the guide you see bellow a long time ago when OpenTabletDriver didn't even exist.
It took me a while to figure this out, so I'm putting this here so you'll have an easier time.
This is for KDE only. I have not used other DEs for osu! so I can't help you there.
- Arch based distro:
xf86-input-wacom
andkcm-wacomtablet