I'm pretty sure I've used CocoaMySQL with MySQL 5. PhpMyAdmin is your other choice, which comes with MAMP and which gives you more controls over stuff like setting users and so on, but the interface isn't as pleasant.
For CocoaMySQL you need to know the root password for MySQL for the utility to be able to connect to it (and MySQL needs to be running), so that you can enter Host: localhost , User: root, Password: <password> in the connection dialog.
I believe for MAMP the root password is set to "root" by default,
.. which you should change (using phpMyAdmin > Privileges > change password for root@localhost), although this may mean that MAMP can no longer connect to it, without altering some conf files 😱