If you don't know what it is, it is so you can have your devs login with out having to get in using your root access, meaning, no OP users in your DB. So lets start
Step one: (we will use Navi) Open it.
Step Two: Connect to your connection you wish to add the user to.
Step Three: Click Manage User. At top right
Step Four: Click add user at the top right
Step 5: Fill in Info
Step 6: Click OKAY
Step 7: Fill in wanted checks