You need to go through all the levels of the second board and do all the objectives. Here is a video made by myself showing you how to handle the different missions.
If you only need a few levels, you can watch the specific video guide below.
Level 2-1 :
Level 2-2 :
Level 2-3 :
Level 2-4 :
Level 2-5 :
Level 2-6 :
Level 2-7 :
Level 2-8 :
Level 2-9 :
Level 2-10 :
Level 2-11 :
Level 2-12 :
Level 2-13 :
Level 2-14 :
Level 2-15 :