Just follow these steps to connect the database:
First you need a database manager that support Firebird conections or some application for this, in this tutorial we are going to use Scriptcase.
Basically, these are the information you will need to perform a connection:
Host/Server address: You can use the domain or subdomain of your hosting service as a address.
Note: If you want to make a access from a application or framework, RAD like Scriptcase that is also hosted in your account you can use localhost(127.0.0.1) instead domain to optimize the connection.
Path: The path until the .FDB file, Firebird databases created in the cpanel are located in /home/MainUserHere/firebird/yourDbFileHere.FDB
Username: The main user of your hosting service, usually called cpanel user, this user is also your Firebird user.
Password: The password of your Firebird user.
How to connect using a Database Manager:
Create a connection
Fill in the connection settings and save.