To play Kevin's bonus levels, you must first unlock them:
Kevin-1: Deliver 2 orders in order in level 1-3.
Kevin-2: Deliver 5 orders in order in level 2-2.
Kevin-3: Achieve a score of at least 1000 in level 2-4.
Kevin-4: Achieve a score of at least 1100 in level 3-1.
Kevin-5: Deliver 5 orders in order in level 4-3.
Kevin-6: Achieve a score of at least 500 in level 4-5.
Kevin-7: Deliver 8 orders in order in level 5-5.
Kevin-8: Deliver 7 orders in order in level 6-4.
Once these 8 levels are unlocked, you must obtain 3 stars in each of them to obtain this achievement. Here are Let's Play (these are guides to get the 4 stars, but 3 stars are enough):
Kevin-1:
Kevin-2:
Kevin-3:
Kevin-4:
Kevin-5:
Kevin-6:
Kevin-7:
Kevin-8: