How to add a person to a group?

Go to: Menu → ADMIN → People Management → Groups

Then you have to choose the group from the group categories list.

Then choose the subgroup to which you want to add the person to. For example, Volunteer services, Computer Wiz-PC. Press on "More details" button.

Now scroll down and look for the person who you want to add to the group. Select the person, and done this person has been added to the group.