Select the Contacts tab from the left-nav menu

Click the Duplicate contacts folder

Select the duplicate contact that you want to resolve

If available, you can auto fix certain duplicates by clicking Auto fix in the top-right

Resolve the duplicate (see below for a guide on each option):

The first account in the list will serve as the primary account/contact after the merge and all other contacts in the list will be removed

Quit: Takes you back to the duplicate overview page
Not Duplicates: Keeps the customers separated
Fix and view next: Merges the customers together
Skip: Takes you to the next duplicate in the queue

This section displays the different contacts and shows the similarity in certain data points such as address, email, etc.

Padlock: Sets the particular contact to be first in the list (primary account)
Minus: Excludes the particular contact from the merge