Facebook Shop allows you to add products via your existing Google CSV feed onto your facebook Business page.
To set this up:
1. Log in to your facebook account and go to your business page
2. Click on 'Shop' via the navigation bar.
3. Click the Go To Commerce Manager button
4. Click to use your website to complete the purchase
5. Follow the set up prompts for your business information
6. Via data source you can select your product feed file to import your products.
> Add products
> User Bulk Upload
> Scheduled feed
> enter feed url e.g. https://www.site.com/product_feed.csv
> Set to Daily
> Set currency
That's it, your products are now available inside facebook.