Q: How can I get a refund for an app that did not download/do not now want

Once you buy it you have bought it and Apple generally does not do refunds.  You can ask but it will have to be an exception.

How to request a refund for an iTunes or App Store purchase - http://www.imore.com/how-request-refund-itunes-or-app-store-purchase

What can be done is try to redownload the app.

Downloading (using iOS or computer) past purchases from the App Store, iBookstore, and iTunes Store - http://support.apple.com/kb/ht2519 - enabled with iTunes 10.3 and newer; not all media formats are available in all countries (see: iTunes in the Cloud, iTunes Match, and iTunes Radio availability by country - http://support.apple.com/kb/HT5085); apps, books (not audiobooks), music, t.v. shows, and movies (some - not all studios have permitted this). Downloading previously purchased movies and TV shows requires iTunes 10.6 or later. Discontinued items not available. For items not included in the iCloud list (e.g., ringtones, audiobooks), or locations or computer systems where iCloud is not (yet?) available, you only get one download per fee paid. Apple recommends, "... back up your iTunes library. " (http://support.apple.com/kb/ht2519). Additional tip at https://discussions.apple.com/message/24176756#24176756 Select the iTunes Store on the left side of iTunes if you have the sidebar displayed, or with the button at the top right. Click on Purchased on the right side under Quick Links (see https://discussions.apple.com/message/26364186#26364186) You can re-download your available previous purchases.