It is recommend to allow setup to connect to the internet and check for updates.
When the update check has completed click Next to continue. This can take several minutes depending on your server's performance capacity.
Setup will detect that this is an upgrade installation.
If you are running load-balanced Client Access servers in a site then you should configure the load balancer to remove the server from the pool of hosts, and allow any existing connections to close, before you install the cumulative update.When the Active Directory changes have been applied, on each server run the upgrade.Cumulative updates can be applied using either the command line or graphical setup, whichever you prefer. Caution: a cumulative update is a full reinstall of Exchange Server 2013.In an elevated command prompt run the following command from the location where you extracted the cumulative update files.The command prompt window will display the progress as the upgrade proceeds.If it is interrupted, or fails part way through the installation, you may need to perform a server recovery.There is also no way to uninstall a cumulative update.The upgrade itself is a lengthy process so you should allow plenty of time for each server.After the cumulative update has been install restart the server if prompted to do so.Note: Exchange 2013 cumulative updates stop the “Microsoft Exchange Front End Transport” and “Microsoft Exchange Transport” services during the pre-requisites check.If you do not proceed with the installation you will need to manually restart the Microsoft Exchange Transport service.