If you would like to add a new user to EventHQ you can do so by going to Settings > Users. From this screen you have the ability to create a new user. There are just a few fields that need completion to setup the new user being their name, email address and password.
The new user will be sent an email with details on how to activate their account.
You also have the ability to assign a role to the new user. Roles for users can be configured on the main user page. These are completely flexible to your own requirements but need to be set before you can assign them to the new user.
You may also wish to allow the user access to all events by checking the box or leaving it unticked which means that you can specify at event level which users have access to that event. This gives you total flexibility over what a user can do and where they can do it!