You can use list groups to organise or categorise lists (e.g. you can group lists according to campaigns or departments). You can see your list group when importing contacts, and on message composition when choosing which lists to send to.
Click Contacts > Lists to go to the list screen.
To create a new list group, click on New > List group and follow these steps:
Click Save when you've selected which lists will belong to this new group.
To edit a list group, check the checkbox next to the group's name in the table on the left-hand side, then click Edit. You can change the List Group's name and add lists to the group. Check the checkbox of the list you want to add then click Save.
To delete a list group, check the checkbox next to the group's name in the table on the left-hand side and then click Delete. A confirmation window will pop up asking if you're sure that you want to permanently delete the group. When you delete a list group, the assigned lists will be ungrouped but they won't be deleted.