Here's an overview on how to create & delete lists as well as remove contacts from lists.
New Email List
You can create lists as you are adding contacts for the first time, but you can also create lists by clicking the plus sign (+) near Email Lists on the left column. Click Email Lists will take you to the List Management screen where you can view existing lists and add a new one by clicking Enter a New List.
Click Add List and it will be added on the left column of your List Management screen.
Delete Email List
To delete a list, click the trash icon near the list you want to delete. You'll be asked if you want you to delete the list and keep the contacts or delete the list and the contacts.
Remember to choose carefully. Deleting contacts cannot be reversed.
Remove Contact from List
To remove multiple contacts from a list, select the list you wish to view from the left column of the List Management page. Click the checkbox for the contacts you want to remove from that list then click Manage Lists and Remove from Lists.
If you have many contacts and want to remove one from an email list, you can always use the search bar at the top-left of your Contact Management or List Management screen.
Confirm the list(s) you want to remove your selected contact(s) from and click Remove.