Typically you will want to have users register themselves by using the public registration page. However Admins are also able to add new users in the Admin Panel and have their credentials emailed to the new user.
In order to manually create a new user, use the following instructions:
Go to the Admin Panel by clicking the Admin button on the top right
Click on the users tab and then click the Plus icon on the top
Fill out the necessary information for your new user. Change the user's role if needed to promote them to an admin user
If needed select the checkbox to email the user their credentials
Click the submit button to create the user