Open Device manager on your PC and scroll down to Portsĩ.
Hold the Volume Up key and plug USB cable in to phone - this will put your phone in to download modeĨ. Using a USB 2.0 Port, connect USB cable to your PCħ. Install LG FlashTool using instructions in zip folderĤ.
Not sure if I can link you to the necessary files, but these are the exact instructions, step by step (You can also check the AT&T LG G3 board on xda for a more complete version of this tutorial):ġ.