In order to edit a product it must first be duplicated.
To duplicate a product, select “Products” from the vertical left-hand menu of your Shopify dashboard. You will be redirected to a list of your created products. Select the product you want to change/duplicate from the list. When the product detail page opens, click on the “More actions” dropdown menu at the top of the page and select “Use product as template”. Doing so will open the design tool. Simply create your new product and sync it to Shopify.
The original product will remain unless manually deleted. Click here to learn how to delete products.