Complete the following steps to install your Server Certificate:
1. Copy and paste the Server Certificate (including the BEGIN and END tags) into a text editor such as Notepad and
save it on your server.
2. As administrator, open Exchange Management Console (Start > Exchange Management Console).
3. Under Actions, select Complete Pending Request.
4. The Complete Pending Request wizard opens.
5. Browse to the location of the webserver certificate file and click Open. 
6. Click Complete.
7. Click Finish.
8. Confirm that the new certificate was imported successfully.
9. With the valid certificate installed, assign it to the Exchange Server 2010 services.
Right-click the new certificate and choose Assign Services to Certificate.
10. Choose the new Exchange server and click Next.
11. Choose the services to assign to the certificate. In this example, the certificate was created for IIS and SMTP. services.
12. Complete the wizard to assign the services to the new certificate. You will be prompted to overwrite the existing self-signed certificate; click Yes to overwrite.
After installing the new digital certificate for Exchange, in some cases, some computers running Outlook displays the error message "The name on the security certificate is invalid or does not match the name on the site" as follows::
In that case, you should perform the update URL to the Exchange in accordance with the following guidelines:
Guide to configure Exchange to use an official domain name (FQDN) instead of the internal domain name (Local name)
After successful installation, you can check the cert was install correctly or not by following tools:
https://cryptoreport.websecurity.symantec.com/checker/views/certCheck.jsp
