I bought a Mac, how do I get rid of linux and install Mac OS again?

I bought this mac second hand. It is an iBook G4, but the people installed linux on it and I would like the OS software on it instead as I have an iPhone and an iPod and iCloud and I would just rather deal with something that I'm familiar with, but I have been looking and I have no idea how to delete it and put what I want on it.

Find the mac os install cd boot up the computer I think you hold down the c key?
and clean install

look up "clean install" mac os online you'll get pictures.

You will need a Leopard (Mac OS 10.5) installation disc. Insert it and Restart while holding down the C key. This will boot from the Installation disc from where you can run the Mac OS installer to wipe the drive and install the Mac OS.

Leopard (10.5) is as high as you can go with a G4 iBook. You will not be able to use iCloud and will only find a limited range of software still works with the old G4 processor.

Will 10.5 support ipod, iphone & icloud? I think the G4 was around before any of that stuff.
Linux is on there for a reason - mainly to extract whatever usability the G4 has left to offer.
Installing a recent linux distro on it means that it is supported ie patched for vulnerabilities and has up to date software on it.
Is 10.5 still supported? Do you really want to be using an OS that old?
Fact is you might be able to install a more up to date linux OS than the linux OS that's on there. Ubuntu would be a good start.
But it's your choice. Try both (dual boot?) and see which serves you best.