How do I rip an mp3 cd to my windows media music on my pc?

You don’t rip it, you just copy the files.

What @pdworkin said. Just open up the CD in Windows Explorer and drag and drop the mp3 files to your hard drive. Then drag them from the harddrive into the “Library” section of Windows Media Player.

But it says it doesnt have any files…

It says it doesn’t have any audio files. You are looking in the wrong place with the wrong application for the wrong files. Close down WMP, and use Explorer to examine the CD for mp3 files. Then either select and drag them to your music library, or copy and paste.