N.B. Foxington only becomes available after beating Jinx and completing the story. Once the Credits have been watched you will be taken there.
To the west of the map you will find the 6 levels you need to beat.
These are marble mini-game levels like those which Tess made you face, but are harder. (still not too difficult)
Near the spawn point within Foxington, just to the right of Lyra (the other fox) you will find a map showing the location of all levels - these are the blue dots.