Depending on your level of subscription you will be able to invite a certain number of co-workers to your team.
Depending on your level of subscription, you will be able to invite as many users as your subscriptions allows. In fact, you can invite much more users than you subscription allows, but at a certain moment, your team will be composed of a maximum of active users.
Go to the TEAM menu bar item and click Invite to team (note that this button will only be available with an active subscription)
After selecting the option, you will be requested to enter the email and the name of the co-worker you wish to invite to your team.
Your co-worker will receive an email and will need to follow the link in the email in order to confirm the account, define a password and be added to the team.
At this point, the user is granted access to the team. He will need to update his profile.