Follow these steps to merge duplicate contacts:
First, in your Contacts tab, select the two contacts you would like to merge into one record:
Next, click the orange Actions button and select "Merge Contacts"
A modal box will appear where you will need to select one contact as the "master record." The bottom contact record will be the master, and data from the top record will be added to it. The top record will then be removed from the system.
To complete this process, click the "Merge Contacts" button.