It’s a fairly simple process to update SCCM SP1 to CU1 level however make sure you have backups of the site server and database before proceeding.
Request and download the SCCM SP1 Cumulative Update 1 from http://support.microsoft.com/kb/2817245
Run the ConfigMgr2012-SP1-CU1-KB2817245-X64-ENU.exe file. Click Next
Accept the licence agreement and click Next.
Address any per-requisite issues such as server restarts. Click Next.
Ensure that the site database update is selected and click Next.
Update all components and click Next.
Click Install to update.
Click Next after the CU has installed.
Click Finish to complete the process.
Any remote consoles will need to be updated.