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