You can upgrade to Pandora One in the Android app by following these steps:
 
From the Now Playing screen, touch the back arrow in the upper left corner of the screen.
 
Go to the Settings tab.
 
Scroll down to select Pandora One.
 
Select Upgrade.

You will then be taken to the Google Play payment page.

On the Google Play payment page, check the box stating that you ‘Agree to the payments for Google Play Terms of Service.’
 
Confirm the purchase by selecting Accept & Subscribe.

Note: If you have a PIN enabled for purchasing, you’ll need to enter that code after selecting ‘Accept & Subscribe.’