When you have obtained the indicated number of Career Points the corresponding Episode will become unlocked.

Episode 3
Obtain 80 points in Career mode.

Episode 4
Obtain 120 points in Career mode.

Episode 5
Obtain 160 points in Career mode.

Episode 6
Obtain 200 points in Career mode.

Episode 7
Obtain 240 points in Career mode.

Episode 6
Btain 280 points in Career mode.