New users are added from the Manage Users page. Try it out: Club Manage Users.
In the "Current Users" section click the "(Add a User)" button. You must provide a name, and optionally an email address. New users go into the sandbox, which is a kind of "halfway house". You can set up data for the user, but they are not fully activated until they have been moved out of the sandbox. As an example, sandbox users they cannot receive emails.
To move a user from the sandbox, they need to be converted to one the following user categories
The UI is very quick and simple, however if you have a large number of users you might find the user import easier.
Newly added users have a default set of permissions: