You get the radio enhancement application from the Kanto Radio Tower and manually tune the radio to the pokeflute channel
u dont. u use the pokegear's music app and move the dot up to the very top in the center
use the app on the pokegear and go to the music thing and go to #20
get the Poke tech App Poke happyness
First Go to power plant and find thief. then go to Lavender city and get Poke flute app then go to radio press the top of circle and boom you've got poke flute
u click and hold the Pokemon with ur stylus
if your trying to wake up snorlax you go to the kanto radio tower get the pokeflute app on your radio(only works if you solved the problem at the power plant)
talk to a girl in the eterna city Pokemon center on 1F
the poke radar isn't an app it is a key item, i think you get from prof rowan after completing the national dex
you have to get a poke app . it shows your pokemons happiness in hearts
at the poke app store in jubilife city when you talk to the president on the right door.
here is the list: http://www.serebii.net/diamondpearl/poketch.shtml
The black flute can be found in Dark Cave in Soulsiver.