Default LG G2 vs 12B problem installing....

installing the root access on my 12B version of Verizon's latest firmware update failed to install Superuser. apk. I was able to install available code which I did line by line...but when I arrived to Superuser.apk this is the message I [INSTALL_FAILED_ALREADY_EXISTS]. Please let me know if there are any alternatives to being able to get a 'complete' root. Although ROOTED shows up in status tab TWRP.