You can open this page by clicking the Side Menu->Admin->Record Merge.

This page allows you to merge any two duplicate records of Candidates, Contacts, or Clients.

In Record to keep, select the candidate, contact, or client record to be retained.
In Record to merge, select the candidate, contact, or client record to be merged with the one selected in Record to keep.

You can click Search to search for a record.
Select the Include Archived check box to include the archived records in the list.

Click Merge Records to merge the selected records together.