How do I potty train my guinea pig?

Ok first of all I know that a bunch of you out there will prob be like ur so stupid u can't potty train a guinea pig! But thats not what I mean what I mean is that any time he need to go potty then he will go to his litter box but not everytime but most of the time hopefully. So now here is the situation: I have a boy guinea pig no older than eight months. He has a pretty large cage compared to his size but I still let him run around for a couple of hours in the kitchen. I lett him in the kitchen cuz it has a hard floor and in case he pees then it would be easier to clean than if he was on a carpet. But the problem is that he pees and poops like EVERYWHERE!! I want him to like go into his cage when he want to pee or poop or just pee or poop in a certain spot so it would be easier to put a litter box. Thanks