You are a group administrator in the chat group?

1. Click on the chat name of the group chat.
2. Click on the participants list.
3. Select "+ Add".
4. Now you can search for the respective persons and add them to the group by clicking on the checkbox.
5. Finally, select "Add".

You are not a group administrator in the chat group?

Contact an administrator in the chat group and ask him/her to add you or another person to the group as described above.

You can find out who is an administrator in a group by clicking on the picture of the group chat and then clicking on Participants. After the name of the administrator, you will see the addition "-Admin". If you are not part of the group, ask a colleague.