Help for single products

I would like to know how can I set the cart notice for single product, these are the 3 products where I need that message to appear but it doesn’t work: https://snipboard.io/DW8ZTP.jpg – these are the links to these products: https://el2.it/prodotto/trattorino-efco-ef-84-145k/ – https://el2.it/prodotto/trattorino-zephyr-72-13-h/ – https://el2.it/prodotto/trattorino-efco-ef-108l-16k/

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