Short answer
Build the JSON-LD for the page type, paste it inside a script tag in the page, then test it in Google's Rich Results Test. The free schema markup generator on this site builds the code for products, FAQs, local businesses and articles. Check first whether your theme or plugin already adds some.
Free tools for this
What schema markup is
A block of structured data, usually written as JSON-LD, that states plainly what a page is: a product with a price and stock, a business with an address, an article with an author. Search engines read it alongside the visible page.
Which types matter for a store
Product, for every product page, with price, availability and a real image. Organization or LocalBusiness, once, on the home page or contact page. Article, for blog posts. FAQPage, only where the questions and answers are visible on the page.
Add what is true and visible. Do not mark up reviews you do not show, or prices that differ from the page.
Try it now: Schema Markup Generator → · Merchant Center Readiness Check →
Where the code goes
Inside a script tag of type application/ld+json, in the head or the body of the page. It is invisible to visitors.
Check what is already there
Many Shopify themes already output Product markup, and WordPress SEO plugins add Article and Organization markup. Adding your own on top can create two conflicting copies.
View the page source and search for ld+json before you paste anything. If a good copy exists, fix or extend it rather than adding another.
Test it
Paste the page address into Google's Rich Results Test. It shows what Google reads and any errors or warnings. After the page is live, Search Console reports problems under its enhancements section.
A warning is a missing recommended field. An error means the markup cannot be used.
Keep it true
Markup that disagrees with the page, such as a price or stock status that is out of date, can lose you rich results. Where prices change often, generate the markup from the live data rather than typing it once.
Also know the limit. Schema makes a page eligible for rich results. It does not guarantee them, and it does not on its own raise rankings. Google now shows FAQ rich results only for a small set of well-known sites.