After you have created a user and a database you must then assign a user to that database in order to access it.
You must also choose which privileges to grant the user for that database.
This demonstration shows how to add a user to a MySQL database and define that user's privileges.
Select the user you wish to assign to the database,
Select the database you wish to assign the user to,
Leaving the tick in the box on the left grants a user access to all privileges on the database OR
tick the appropriate boxes on the right to choose specific privileges for a user,