How to log off iCloud on my iPhone 4?

I have the 4s update I think, haha yeah I've had it iphone 4s came out and I haven't updated since because memory is so full to the point I can't even take pictures off my phone anymore. But yeah my phone is on my stepmoms iCloud account and I don't want that because it backs up to her account. I need to it on my iCloud not hers, does anyone know how to log out of an iCloud so I could get off my stepmoms iCloud and get on my account?

Yes it's very easy,

1. Goto settings / iCloud
2 go down till you see " delete account"
3 this won't delete the account, it just logs you out
4. Everything from that account will be took off you iPhone
5. Now you can login to a different account