See here How to Add SEO Tags to Your Shopify Store.
1: Access Shopify Admin
Log in to your Shopify admin panel.
2: Edit Online Store Preferences
Navigate to “Online Store” > “Preferences” from the sidebar.
3: Fill Meta Title and Description
Enter relevant SEO meta title and description for your store.
4: Add Tags to Products and Pages
Add SEO tags such as meta keywords, alt text on images, and relevant product tags.
