pro chrono bluetooth digital app / Amazon Fire tablet

Bought a Amazon Fire tablet thinking i could down load the pro chrono bluetooth app to it to keep my chrony records for my air rifles.
What I didnt know it seems these are set up to only use Amazons app store and when I try to download app it doesnt recognize the Fire tablet as being a device to download to, my Android phone comes up but not tablet.
Has anyone on here managed to get this app to download on the Fire tablet, if not then I just wasted 65 bucks for this thing. Appreciate any help.
 
Amazon Fire tablet has access to a limited selection of apps, so if you can't find a specific app in the Amazon Appstore, you may need to sideload it manually.
I have the permission allowed to use a 3rd party app or whatever its called, but when I go to download the app the tablet will not come up as a recognized device..I can usually figure this crap out but Ive run out of patience messing with it, will get a small laptop later and use it. Ive read even if you do get the app to download that Amazon has so many obstructions to prevent it that it can cause device to freeze or quit working completely.