Here's the link to the product support webpage for your TV. The full manual can be downloaded here (Click "Support," and the link is under "Documents" on the right side of the screen.)
From the manual, here's what it says about cleaning:
And in order for the TV to recognize your wifi, you'll need to plug in a wireless network adaptor to one of the USB ports. (network adaptor sold separately.) Follow these instructions to establish a wifi connection, and then follow the on-screen instructions for wifi/network settings. Or for details on how to adjust your wifi/network settings, see pages 58 and 59 of the manual.
That's kind of hard to read, but it says.
"The LG Wireless LAN for Broadband/DLNA Adaptor, which is sold separately, allows the TV to connect to a woreless lan network.
The network configuration and connection method may vary depending on the equipment in use and the network environment. Refer to the setup instructions supplied with yur access point or wireless router for detailed connection steps and network settings.
1. How to connect
Connect the "LG Wireless LAN for Broadband/DLNA Adaptor (sold separately) to the USB IN 1 or 2 port on the TV.
2. How to use
Select "Network Setting" in the NETWORK menu
After connecting, you can use the NETCAST menu"
Best of luck!