Here is a simple procedure how to update firmware on UCS C200 M2 server. The procedure should be no different on the other models of C series servers as they use Host Update Utility(HUU).
1. First you need to download the firmware for the upgrade. In this instance the server will be upgraded to 1.4(3p)5

• Go to Cisco.com, select Support and All Dowloads 
• Choose Servers- Unified Computing and Cisco UCS C-Series Rack-Mount Standalone Server Software. Select your server model(in this case it is C200 M2)
• From select Software type choose Unified Computing System (UCS) Server Firmware
• Find the required version and download it(you’ll need to login). It will be iso file:

  

2. Mount HUU iso in CIMC (more…)