What app do I use to play the various sounds that I have downloaded from Arturia
If the sounds is for Arturias software instruments, then you in example can import them in Analog Lab. Then they can be played in Analog Lab, and in the application where the sounds originally is made.
If the presets are from the sound store you ie can install them through the Analog Lab application store.
If the sounds are for Arturias hardware instruments, then you need to have the hardware to use them.