In the following example we'd like to add two tabs to our product. One for About and one for Image Size.
First, we navigate to the product page in our Shopify admin section. Here you can see the description of the product - this where we will add our tabs by simply changing the formatting of the text.
To add a tab simply highlight the phrase you would like to make a tab heading. In this case - About and Image Size. Then change the formatting of each phrase to Heading 4 and finish by saving the product.
The product will now be displayed with About and Image Size tabs.