This is step 4 of the local inventory onboarding guide.
To show your local products on Google, you will need to link your Business Profiles to your Merchant Center account and select a business group. The Link Business Profiles and Merchant Center article explains how.
Note: Your stores must operate with a storefront that is physically accessible to customers. As a result, your Business Profiles need to reference an address. Learn how to add an address to your Business Profiles