These steps will walk you through assigning an existing third-party SSL certificate to the Exchange services such as IIS, SMTP, POP, IMAP and UM. These steps assume you have already completed a certificate request and installed your SSL certificate on Exchange 2013.
Step 2: click “services” and then place check marks next to the services that you would like assigned to the SSL Certificate. SMTP, IMAP, POP and IIS are standard. Note: If you have a Wildcard SSL certificate then leave IMAP and POP unchecked, Wildcard certificates do not work for POP/IMAP.
Click “yes” on this standard warning message which indicates the default self signed cert will be replaced with your new third party SSL certificate.
Conclusion: At this point your SSL cert is installed and enabled on Exchange 2013. Congrats! I recommend you test your certificate by connecting your server with a Browser and see if any errors come up: https://servername.domainname.com/owa
Next: you will configure the Exchange 2013 Virtual Directories.