Automate to batch resize and place on background for Instagram

Hello, I have figured out how to create an action to open a black square, place an image, and then save it to a specified folder. I created a droplet so that i can drag and drop images to the droplet to quickly process files for social media. However, instead of processing the diffferent files, it always process the same original file used in creating the action. How do I make this action relative to the files I am dropping on the droplet? Thank you.