In order to use Google Ads to promote your Shopify store and products, you will want to follow this guide. You will need to install the Google Channel on your store, as it integrates with Google Merchant Center and Google Ads.
Doing this will allow you to create Shopping Campaigns (paid advertising that can help you to promote your products and increase traffic to your online store) and you can manage and monitor your Smart Shopping campaigns from the Marketing > Automations page in Shopify.
As well as running Google Smart Shopping campaigns for specific products, you can also run a campaign for your whole product catalog to improve the performance of your Google Smart Shopping campaigns.
I hope this helps! Let me know if you have any other questions.
All the best, Hyde.
Andrew | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog