This will come naturally by just playing through the game, however if you want to get it quicker (Hello TA hangman players and everyone doing a community challenge that requires you to get a V!) I found that the fastest way for me, as a player who tends to crash on crowded tracks, was to go onto:
Event type: Race
Location: Hazyview Oval
You get 60 experience for each lap you complete without crashing, plus if you take your fastest car you should be able to maintain 'high speed' for extra experience too. Stay on the best line and that experience will also add on. I found a lap for me in a fully upgraded A class car took around 18 seconds on average.