How do I get a paid app onto my iPhone when I have downloaded it to my iPad. The app has a license for 5 licenses

Hi

I am a newbie to paid apps, and have previously used freebies. I have never quite understood the mechanics of how the iPad and iPhone are meant to keep the apps in sync. I've paid $150 for a Hema mapping app which I downloaded to my ipad ok. The license covers up to 5 idevices. I'm stuck on how the app is meant to "appear" in my iPhone.

I've googled, searched apple forums, and the best I get is the brochure ware on the apple page which says that things are meant to appear in one device if they are downloaded to another (or something similar to that). Can someone take the time to explain what I need to enable to have this happen, and/or what I need to do to get the mapping app onto my phone if enabling a feature doesn't retrospectively "sync" my devices.

I have a iPhone 4, iPad (

Thanks so much.