Chris Hoffman, writing for How-To Geek, walks you through the refund process.
I found this interesting:
Apple only allows you to request a refund for purchases you’ve made in the last 90 days. Unlike Android’s Google Play Store, which offers a two-hour no-questions-asked refund period, Apple doesn’t offer automated refunds in the same way. This isn’t meant to be a feature that allows you to trial paid apps, although Android’s refund feature can be used in that way.
Bookmark and pass along.
I have never had any trouble with asking for a refund on the iTunes store or App Store. As long as you are reasonable, they are usually very helpful.