What App Do I Need?

I have no knowledge sorry, I use Dealer Tool, it's straightforward to use and covers everything you need for servicing.

 

You need android bud.
I had to buy an old cheap phone just for that purpose as I had a crapple too.

 

Maybe try the OBDLink app, see if it is compatible with your reader, the android version can at least read and clear fault codes
https://www.obdlink.com/obd-apps/obdlink-app/

 

Very unlikely to work tbh as the amazon sw is a heavily modified form of android.
https://www.howtogeek.com/232973/amazons-fire-os-vs.-googles-android-whats-the-difference/

 

Scrub OBDLink, start page claims it only works with their readers.

 

Not sure at all but, if it’s code reading, try Ross Tech.
Not used them myself but if the stick thingy gives a code number, they may show on their website.

 

I use TuneECU on Android after realising it wouldn’t work on any of my Apple devices