1. Click on System Config > Account Types from the left menu.

  2. Scroll down the page to search for and click on the Name of the Account Group Field you want to add accounts to.

  3. Go to the Groups tab.

  4. Select the number of groups you wish to add and click Add More Groups.

  5. Enter a Description for each group.

  6. Save Changes to add your groups.

For further information on how to add accounts to groups, you can read the article Adding/Removing Account Membership of a Group.