Can't install to my .com/ database


I can’t get users to see anything at the default database.

When I try to do a 1-click install to it, it fails, saying that that database isn’t empty. If I have concrete5 installed on a different data base
can I use that to put any links or banner or anything on my just plain

I can’t figure out why I seem to have no control over the domain unless it has something to the right of the slash.