How do I cancel/delete unwanted icloud email accounts?

I have an iPhone and a PC, which I wanted to synch via iCloud. I went through the necessary steps, and everything worked fine..... the equipment is synced. BUT THERE IS A PROBLEM. The system keeps putting a box on my computer screen that says I cannot do anything (and I cannot remove the box) until I provide a password for an email account (actually two accounts) that I didn't even know existed. One account has my wife's nickname@me.com; the other has my wife's nickname@icloud.com. (Apparently, when they sold us the phones, someone opened these accounts for her on MY phone (accidentally, I'm sure) without showing/telling what he had done.

I MUST GET THESE ACCOUNTS DELETED, but nowhere can I find instructions that will show me how to do it. There's a friendly message telling me that these accounts were automatically reserved for me when I put myself on iCloud..... and the message says that I don't have to use either...... but it doesn't telll me how to delete them so I can start using my computer again.

HELP!