Got Questions? Ask here
It's pretty much at the top, so it's not that hard to miss.
As for your question, Mobage have changed it so you have to look for the offers instead.
Click on the Mobage logo at the top left corner to open up your Mobage profile page.
From there, it should show you a set of images under the title 'Find Games' and you can scroll through them which ones offer you how many Moba Coins you can get from installing and playing them.
Do note that this only works for Android users.
All iOS (iPhone) users miss out since they use Fanta Coins, and also they get discounts on their gift cards.