You can add more team members if you are the team admin.
1. Tap Contacts
2. Go to the Teams tab, and select your team from the list.
3. Tap Add members.
NOTE: When you are in the Message tab, you can tap on the team name to access the same option of adding members.
4. Enter the name or the email address of the person/s you want to add or select from your contacts list.
5. Tap Next.
Personal contacts will receive an invitation to join via email. They will be able to participate fully in the team conversation when they join.