To create a new admin user, follow the steps below. Note that you must be logged in as an admin user with manager privileges.
Go to Users > Create User.
Fill out all fields appropriately, including passwords (you can put a placeholder here, and then send the new user a password reset email--see below).
Click 'Create' at the bottom of the page
(Recommended, but optional) Send login information to the new user, by clicking on the 'Send Login Information' button that will appear after creating the user. An email will be sent to the new user with a time sensitive token (usually about 24 hours), allowing them to create a new password.