This can easily be a trophy that you can obtain straight away in either of the campaigns.
I got it in the trader campaign, when you start up and you're in the city view of Port Royale, simply find the church and select it, you will now have the ability to press
to pray, simply pray 10 times and it's yours.
Or if you don't want to spend time praying at one church, every single town should have one, and there's 20+ towns in the game so there's more than enough, it doesn't take long doing it in one, enjoy.