Login to Your Hosting Account
Access Your Database Area
Create a New Database User
Be sure to take a careful note of your password.
Add The New User To Your Database
Make sure to choose the correct user and the correct database, then click "Add".
Give the New User All Privileges
Login To Your File Manager
Open Configuration.php
This is the file that connects your Joomla files to your database. It needs to have the correct username and password.
Update the User and Password Details
Scroll down until you see the $user and $password fields. Insert the information you created earlier. Then click "Save" and check the front of your site to ensure everything is working correctly.