If you have just created an Account in Regular.li or just created a Location in your Regular.li Account, there will see a banner on your Dashboard with an ADD USER button. Click on the button to open the User Creation Form. Fill in details and click the ADD button. Click here to see a small tutorial on Adding Users.
You can also go to Menu, click on Members and hit the Plus (+) button to add Users/Admins/Super Admins. To watch a tutorial on Adding Members click here.