Login to Your Hosting Account
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Access Your Database Area
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Create a New Database User
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Be sure to take a careful note of your password.
Add The New User To Your Database
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Make sure to choose the correct user and the correct database, then click "Add".
Give the New User All Privileges
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Login To Your File Manager
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Open Configuration.php
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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
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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.