To access the "My Tracks" section, tap play.
Then tap challenges.
And finally tap my tracks.
You have the option to filter tracks between three categories: Time Attack Tracks, Track Packs, and Premium Tracks.
Locate the check marks under the three symbols to the left of your screen to toggle between the categories.
The stop watch is the "Time Attack Tracks" you have beaten in career; The open box is the "Track Pack Tracks" you have bought in the store; The premium star emblem is the premium tracks.