Ah, so it's not quite phpMyAdmin. I see two options. You can see if you're able to SSH into your account to access MySQL more directly and use the link I provided earlier, though it's quite possible the host has limited the commands you can use through the command line.
The second option, is to open the sql file and edit it so it skips the database creation. It should be a plain text file and that should be very close to the top of the file. If you need help you can post part of that file here. Not sure how large it is so not sure if posting the whole thing would be a good idea. You could edit it so it checks if the database currently exists.
Code:
CREATE DATABASE IF NOT EXISTS dallas;