Since the service packs are cumulative DBA’s don’t need to upgrade to SP1 and then upgrade to SP2 to get to SP2. Below are the steps to do the upgrade.
Go to the location where the SP2 application file is downloaded.
Double click on the application.
Click on Run
Click on Continue
Click on Next
Accept the License terms and click on Next
Select the features and click on Next
Ensure that no processes are in use. Identify if any of them are running and then stop and disable any logshipping or replication jobs temporarily until the install is completed. Do a refresh check if any processes are identified as being used after you gracefully end those processes.
Now click Next
Click on Update
Hope this helps!