What we're doing
The template you copied came pre-loaded with sample products (door signs, coasters, earrings) so you could see the app working end-to-end. Now we replace them with yours.
The order matters slightly. We do categories first, because every product belongs to one. Then basic products. Then parents and variants if you have items that come in flavors (sizes, colors, months, scents). Then bundles for "X for $Y" pricing rules.
If your catalog is simple (no variants, no bundles), you can stop after Step 2.
Most vendors fill in the basics, work an event, then refine. Cost numbers, FavRank, ImageUrl, all of it can be filled in later. Get a rough catalog working first, polish over time.
Edits in Google Sheets don't show up in the app instantly. The app reads from a local cache so it works offline at the booth. When you add or change rows in the sheet (categories, products, bundles, anything), open the app, go to Settings → Pull from Backend Now, and the changes load into the device. If you don't pull, the app keeps showing the old data and it looks like the edit didn't take. (Changes you make from inside the app, like the Edit / Add product or Edit bundle forms, sync automatically and don't need a pull.)
All four steps
Each step takes 10 to 20 minutes depending on how many products you have. You can jump to any step using the strip above (or the same strip at the top of every step page).