How do I upload the .mdf file and associated .ldf file from visual studio to a host using WebsitePanel?
You can check with them, but it's highly unlikely this method of connection is supported by the host.

The preferred way of getting your database set up is to restore a backup (you can do this through WebsitePanel), and follow their instructions for connecting. A host will normally have example connection strings that you can copy/paste into your configuration file.