some general informations first:
Version 1 of Free Stock Search works in Photoshop, InDesign, Illustrator, Premiere Pro and After Effects.
Version 2 works only in Photoshop (reason is that the underlaying new technology UXP currently only is available in Photoshop)
For version 1 you don't need to install it for all apps seperately. You install it once and in all apps you can find the plugin under "Window" > "Extensions".