This app was very helpful to us. Our facebook page for DriveSafeRideSafe, now has a tab where all our products show up. I'll share a few specific hints from my experience.
1. Even though you're downloading the app for a business page on Facebook, you still have to be signed in to Facebook first as a PERSON. So don't worry that you're about to somehow put this in the wrong place because of that confusion. Log in to Facebook as yourself. Then download the app from Shopify. It's not going to end up on your personal page.
2. We have 3 collections, but I wanted my Facebook visitors to see ALL our products at once, instead of seeing them as different sets to click through. I was not convinced that they'd really notice the drop-down menu option, and the collection that I would have preferred to show up in front, was not showing up that way. Here was my peculiar solution: I created another collection in our Shopify store that includes ALL our products. It's actually HIDDEN in Shopify; it is not visible anywhere in my navigation on our storefront. But this app still let me choose that Collection! And it shows up just fine! That works great for my purpose; it lets me have a page on Facebook where ALL the products show up, but that choice is not on our normal website, where it would create confusion.
3. My final tip: I was able to make the tab with our products show up in Facebook as the 2nd tab under our banner graphic, but I was concerned that visitors might not notice it. Facebook seems to require the first tab to be "Photos" ....... so I created a graphic that is an arrow pointing right, and uploaded it as our most recent Photo. That forces the visitor's eyes to notice the 2nd tab, which is a graphic that invites them to click to view our SOLUTIONS. If I upload any other photo, that will default to the Photos box, but I can always re-upload my arrow graphic again to keep that visible in that spot.
Hope some of that is helpful to other folks.