This mode is locked at first launch of the game, you will have to finish all 3 chapters of the starter tracks and get to collection level 3, you must get it at end of Chapter 3.

First, play on multi-player mode


Than click on Local free play, and on 1 Player.


After that, choice the tracks you want between the selection


After that, choice some option like the IA difficulty (5 choice between Really Easy / Easy / Medium / Hard and Really Hard); number of IA Players (between 0-7), numbers of laps and the Cars speed (Fast corresponds to a racers at Level 15 / Faster to a racers at Level 30 / Very Fast to a racers at Level 45)


In this mode, you can play will all differents racers, even if you don't unlocked them, you can see all of them in the little Icon "See"


After that, make you're selection and launch the race :)