Users are configured in the Management tab, under the Users subtab.
Click the green Add icon to add a new user.
Choose a user name and password. Enter an email address to allow the user to set their own password. The user can click the "forgot password" link at the sign in page to have a password reset link sent to their email address.
Navigate to the Roles tab.
For full access to EnGage, the only user role required is Network Admin. Assigning additional roles will not add any permissions beyond what the Network Admin role already has (With the exception of OnSite roles)