What is a MYSQL Table (Prefix)? How do I use this with OSTICKETS

I'm trying to install a contact ticketing system osTickets

I don't have much knowledge at all of SQL, I've created a database and a username (linked them together).

I'm getting an error message:

Unable to connect to MySQL server: Access denied for user 'part-box_ost'@'localhost' (using password: YES)

Maybe this is because of the MySQL Table Prefix?

See below

What can I do? Do I need to create a Table? if so what do I add?