To set-up delivery in your Google Merchant Center, select Products and shop on the left hand menu, and click Delivery and returns:

You then need to select the Add delivery policy dropdown and choose Delivery for online products:

Name your delivery policy and select the Countries that it applies to, and click Continue:

On the Products page, select All products and click Continue:

After setting the name, region and products, you must set the Delivery times. This includes both Handling time and Transit time. It is important to be accurate with these listings, including the days which orders are Fulfilled and Dispatched as it will affect the shipping times shown on your Google product listings.

Finally, set your Delivery costs. Set the Currency for your region, and decide if you want to add a value for Free Delivery by setting the Order value conditions. Then select a Delivery cost type that matches the setup on your website – this is most often set by Weight.

Once all details are set correctly, select Save in the bottom right. Your products will then be eligible to show on both free Google product listings, and Google Shopping adverts.