You need to be the owner or an admin of a project to invite other users.
1. On the Projects screen, tap on the 3 dot icon next to your project.
2. In the Project Settings, press the Project Members/Invites button.
3. Press the Invite New Users button.
The users that have access to the project or have been sent an invite are listed below the invite button. You can remove access to a user by tapping on the delete icon next to their name.
4. Type the email address of users that you want to invite and press the Invite New Users button. Invitees will receive an email invitation to join your project.
When inviting existing users of your organisation to a project, you can just type their name to quickly find them.