Adding SKU data to procucts

I’m looking for a way to add the SKU for each of my products in the shop. I would like it to appear on both the catalog page and also the single product page. Is there a simple way to do this? I have seen on several different sites that you can edit the SKU number for each product by going through Products>Edit>Product Data, but there is nothing in that section that has anything to do with SKUs. I know the SKUs exist because our orders display them, but I can’t find anyway to add them to the page.

The page I need help with: [log in to see the link]