this is a pretty easy achievement to do
open your map and look for the 'horizon tour' sign ( should be slightly north east of the horizon festival mexico sign)
you can either fast travel to the sign or just set your waypoint and drive there
once there you will be prompted to press x
from here you will have a countdown and then will be put into a race which is you and some random people against the ai
after doing the first race (win or lose doesnt matter) you will be given the achievement