Under the Request, Install or Assign Certificates section click Run.
Choose External Edge Certificate and click Import Certificate.
Use the Browse button, and locate your certificate file (will be .pfx if you used DigiCert Windows Utility. If using a .pfx file be sure to check the Certificate file contains certificate’s private key checkbox). (Will be .cer if you use the Lync interface to create the CSR).
On the Executing Commands page ensure Task Status is completed, and click Finish.
When returned to Certificate Wizard main page, click on External Edge Certificate, then choose Assign.
On Certificate Store you can choose Next, or view the certificate if you’d like to verify you’ve installed the correct certificate.
11. On Executing Commands page ensure Task Status shows completed, then click Finish.
12.To verify your certificate has been properly installed, look at the status column to ensure the External Edge Certificate is showing Assigned.
Import from PFX
If you’ve already created a certificate on another server, use the following instructions to import the certificate in a .pfx format to Lync 2013.
Select External Edge Certificate and click Import Certificate button.
Choose the PFX file and enter the password.