A group admin or a group owner can delete a participant from the existing group.
To delete a participant:
Locate the group from which who wish to delete a participant.
Click on the group name or profile picture at the top of the chat window.
Or
Click on the ellipsis icon and then click Group info.In the Group info screen, click the ellipsiscon next to the username and click Delete participant.
In the Remove participant confirmation box, click Ok.
The participant is deleted from the group.