A user can be added directly to a private chat group by a group admin or can request to join a group as detailed here. Managing join requests can be done by the group admin.
Note: If a user is added to a group by a group admin there is no requirement to accept or reject any invitations as they will then automatically appear in the group and receive messages from the group admin.
To view join requests
Open the Chat group and click on the settings button (3 dots on top right).
Click on group info to view any new requests.
Accept join requests
Select the accept button for the corresponding join requuest and this user will automatially join the group and view messages.
Reject join requests
Click on the reject button and you will be prompted with an option to provide a reason for rejecting the join request.
e.g: This group is for parents of the U12 team only.