You shall not 'insert the user into the database'.
You have assigned all global privilges to user 'admin'. So now the user 'admin' can do ANYTHING with ANY database on the server. So just enter details for user 'admin' at the connection screen.
But do you think it is clever to create so a powerful user ? There is the ROOT user available already when you need to have all privileges. But that is rare …
From tools .. user manager .. manage permissions you can assign privileges to databases, tables or columns individually. Maybe that was what you were after ?
For instance with a fresh MySQL installation a user 'test' is created who has all privileges to the database 'test' (also created by the installer – but starts as an empty database) and only to this database.