Working in a team is great, and we encourage you to invite the people you work with!
To invite new team members in the mobile iOS app please follow these steps:
Click on the Contacts button in the bottom right-hand corner.
Once you are on the Contacts page click on the Add a Team Member button in the upper left-hand corner.
Choose either to invite the users from the Contacts on your phone or invite a new user via the email. To invite via the email simply type the user's name and hit Invite.
The user will receive an invitation via email and will need to accept it by following the link within the email.
Once it's done, you are good to go!
Enjoy collaborating :)