Please follow these steps.
Step 1: Copy the embed code of the product for the ingredient widget.

Step 2: Go to the Shopify Product page, click on the product you want to add to the ingredient list to.
Step 3: Under description, click on the "<>" symbol to show HTML.
Step 4: Paste the code you copied earlier in the box.
Step 5: Click on the "Preview" option to see if the widget is implemented successfully.
Step 6: Now "Save" the changes.