Error when creating a Database connection

Hello:
I am trying to get set up. I am VERY confused and new and since I only have 13 days left to get somewhere, I need some hand holding. (sorry)--
Running on a Mac 10.5.8-DWCS4. It looks like I have successfully set up the local database.

1.But why are there two carts? (crankyduck_cart) INSIDE is another folder of the same name.
2. I do not understand how to set up the DM file so that it finds the local database. I created a php file named teeshirts. I'll worry about uploading files to the real server later--I just need some guidance on how the software works.

I really need some one on one help if anyone can walk me through this?

Thanks