Open the documentation and navigate to:
PlayStation(R)Mobile SDK -> Related Pages -> User Guide -> GameEngine2D

There are also examples for Physics2D, In-App purchasing, On Screen Controller etc.

You're might in the wrong documents.
The documentation installed under this path for me: C:/Users/Public/Documents/PSM/doc/en/index.html

Open the documentation and navigate to:
PlayStation(R)Mobile SDK -> Related Pages -> User Guide -> GameEngine2D

There are also examples for Physics2D, In-App purchasing, On Screen Controller etc.

You might be in the wrong documents.
The documentation installed under this path for me: C:/Users/Public/Documents/PSM/doc/en/index.html