Navigate to the Contacts tab and ensure you are in the Smart Lists tab here

Find and select the contacts you wish to merge together

Click the merge contacts icon (this is the very last icon under your bulk action options)

You will then be prompted to select a master contact. You can then select the information for each contact you would like to merge across into the new contact

You can then select ‘show all fields’ to drop down all additional fields where you can again select the relevant information you would like to merge across into the new contact

Once this is complete, type in CONFIRM and click ‘Resolve’

This will then merge the contact and bring up the contact card for this new merged contact.