How to assign user to group?

Make sure the group is already created in the portal. Administrator > Home > Group > Add group.
Sign in to the portal as Administrator. Go to Users.
Search and click the user you want to add to the group.
Go to the Groups tab.
Search and click the “+” button at the right of the group name.
The group member badge will appear next to the group name and the “+” button will be changed to “-“.