There's a couple ways of doing it.
You can either hook up yout TV to the internet with by WiFi (if you have the option, not all of them do) or with an Ethernet cable. Your TV should automatically update, but you you may have to go into your settings and set it up to.
OR you can go to LG's website and see if there's an update available and download that onto a thumb/flash drive. Plug that into the USB slot on your TV and you should be good!
Either way, there should be instructions either in your manual, or on the website.
Let me know if that helps!