In order to "Manage" or "add" groups I need to know the following:
What are groups? How can they be used?
The CiviCRM documentation provides a good rundown of groups and tags (and the best way to utilize each): http://docs.civicrm.org/user/en/4.6/organising-your-data/groups-and-tags/.
One of the great things about Groups is the option to use Smart Groups that automatically add contacts with certain attributes to a specific group, rather than you needing to remember to add each individual one.