some apps, no problem loading on 2 devices. Not this one - help I have loaded a free app (imediashare) from Amazon store onto my Kindle Fire. I want to put the same app on my Samsung phone, but when I go to the app store from the phone and try to 'buy' it, I'm told I already own it. 

I have had no trouble doing this same action with some other apps, nor with any books (putting them on both devices)

I think I may be able to reload it from my apps library, but I cannot find it, navigating from the Samsung. 

Any help would be much appreciated.
This article should help:

How to install paid apps on multiple Android devices

Also you can try to install application using web version of Play Store (in the Send to list select needed device, for example, your phone).