Just do /register [PASS] <==TYPE THE PASS YOU WISH TO HAVE IN HERE.
When you need to log in, do:
/login [PASS] <==TYPE THE PASS YOU HAVE REGISTERED WITH IN HERE.
Type without [ ]
Also you can change name and password with the commands:
/changename [NAME] <==TYPE NEW NAME HERE.
/changepass [PASS] <==TYPE NEW PASS HERE.
Always without [ ]
It is not allowed to have more than one account. If you get caught with more than one accounts you will get banned.