You can add as many users to your team account as you like.
For a team member to be added, they need to have registered as a new user via this link.
Once registered, you can invite them to your team via the team tab of your admin's account.
1. Click on 'Members' and then on 'Add Member'
2. Type in the email address with which they registered
3. Click on 'Invite'
The new team member will receive an email and invitation link. Once they accept, they will be part of your team.