FOr OS go to options icon>About. I am running 4.3.127 (VZW) and can see YT. I know that once 4.5 is released for your device, you should be able to see it.
I am sure your carrier has a website to D/L the OS. once this is done make sure you have the Desltop Manager (DM) as well. Install the OS update and it installs via the application loader in the DM. Make sure you need to do this first, you need to know what version you have on the device.