Creating new users can be done by admins (members of the admin group) only. In order to make a user an admin, simply add them to the admin group (on the groups menu).
To create a new user, click first on Settings, then on Users to get to the Users menu.
Inside the Users menu, click on the + New User button:
For this example, we will create a new user named Morpheous.
Click on the +New User button and fill in the name and email of the new user:
After filling in all the details, click on Create User and you should see the confirmation box where you can also find a manual invite link (in case you didn't set up the email properly, as shown in the following example):
Congratulations— you've just added another Redash user to the system!