In your account, go to Contacts — Lists.
Open the list you need. Tick the contacts you would like to move or copy.
You can select all contacts on the page or in the list by ticking the box on top next to Email, or particular contacts by ticking the corresponding addresses.
When the contacts are selected, you will see the Acions button. Click on the button and choose the Add to Lists option (if you prefer to move them, choose Move to a List).
Then, in the new window choose the lists you would like to add the contacts to (2) (if you need to find the list, enter its name in the search box (1)).
To confirm the action, click on the Add button in the bottom of the page.