Missing Realms

When I log in, the only realms I can select are the WotLK 5 realms. I downloaded the Mists client, though I have a WotLK install on my computer (separately) as well. I'm not even sure 5.4.8 will work on Wrath servers. Is my problem with the other install or something else?

You should not see wotlk realms with MoP client. Are you using the right client? When you launch it at the bottom right corner you can see what patch it is. What does it say?