You can use bulk actions on the Shopify Products page to make all Online Store products available to the private app (Storefront).
Steps:
1. Tick the master checkbox next to a drop-down arrow to automatically select all the products from your store.
2. Click Select all 50+ items from your store (Available for products more than 1 page)
3. Click the arrow down for More actions and select Add available channels(s)...
4. A pop-up window will appear. Tick the box next to the app "Storefront" (or other name). Click Make products available.
Note: Performing bulk actions on 50+ items can take a few minutes. If you have selected all list items for a bulk action, then wait for the bulk action to complete before making other changes.