If you are doing this legit this could take a few tries, if you are boosting with a friend it will be considerably easier.
Start by going to
Challenges, then pick
Solo, then pick
Create.
It will then come up with your list of last events, pick the one you want to create as a challenge the pick
Add Recipients.
Now either send it to a Friend on your list who has the game or send out to random Driveclub gamers, now either your Friend or the random person has to at least compete in your challenge for it to count, so then you must make sure that once the timer ends on your challenge and you are at the top then you will get the trophy.
Along with this trophy:
So obviously getting a Friend to help makes this much easier than randoms.
Feel free to message me if you want help with this trophy.