Linking Shopify catalogue to a FB business page shop

[RobbyC]

I am trying to link my Shopify store to a Facebook Page. So I have a shop on FB and IG

I can find a link to edit an Action Button to add a Shopify site. Once I select Shopify I am taken to shopify.com to install the FB/IG app. This is already installed.

From there I cannot find where to go and how to get them working together. I seem to go around in circles within the Commerce Mgr.

Help please. Cheers