I'm new to all this, and I have NO IDEA what I did wrong, or what happened.
I was trying to use the SMF Default Theme - Core, and when I had clicked to another theme (I think it was Babylon) everything went wrong.
I can't see any of our options.
This is what it looks like:

I just can't figure out how to fix this problem because I can't click on anything.
When I go to the main admin page up at the top it says: This default theme's directory is wrong, please correct it by clicking this text.
When I click it, I get that blank page again.

I just don't know what to do!! Please help?