In order for your users to add any store items to their gift list, you need to add “Add to Registry” buttons on your product pages. This button will by default display in all your product pages. To whitelabel your add to registry button, you can change the button color and text during onboarding screen after following the below steps.
1

Go to Shopify Theme Editor

From your Shopify admin, go to Online Store > Themes. Select “Customize” to go your current theme’s editor.
2

Go to your product template

Navigate to your default product template.
3

Check if your store template is Online store 2.0 or Vintage theme.

Look in the sidebar, below the product template sections. Check and see if there is an Add section button appears below the section list.If you have an Online Store 2.0 theme, then an Add section button appears below the section list. Go to step 4.If no Add section button appears, then you might have a vintage theme. Go to step 5.
4

Steps to add the button if you are using Online Store 2.0 theme

5

Steps to add the button if you are using vintage theme

6

Hit Save