Alright so im not responsible for any damage to your phone yadda yadda.
Alright goto:
www.bitpim.com goto download and download this one:
BitPim Test Release 1.0.7.20081215 (15 Dec 2008)
goto settings in your phone then connection, then USB COnnection Mode and select Data service.
Plug the phone into your mac via the USB Cable (plug it into the back not the keyboard) and open Bitpim. Goto the "bitpim" thing on the top bar (beside the apple) then prefercenes. On "Phone type" select LG-VX8700, then under "Com port" click "Browse" and click the one that looks like this (Highlited)
then click Ok.
Now goto "View" then 'View Filesystem", now on the left menu bar click "View Filesystem" then double click on the "/" File then just wait a few seconds (30 seconds to a minute Usally) (it will say "Retrieving..." This is good!) Now double click on "LGAPP" then "Media" then "Midis" then "Ringtone". Then add the file there!!! Keep the file under 300kb! You can get and make good ringtones from:
www.cellsea.com (its actaully really good)
wait for it to complete then gointo your phone goto settings- Audio & Ring Tunes- ringtunes- then find your file then press set!!
THERE YOU GO!!
Reason i did this is because i couldnt find a method that worked with my phone so i found this one and it worked!!
DO IT AT YOUR OWN RISK, IM NOT RESPONSIBLE FOR ANY DAMAGE. Ive never heard of any problems before but just incase.