Before we go any further it should be noted that this root method is specifically for the H918 variant of the LG V20 and requires your phone to be bootloader unlocked (won't work on Verizon). That being said the method is actually pretty simple for those who are good at following directions. The root method also installs TWRP as it roots your phone. Head to the link below for the full instructions and download links.
via XDA