Problems connecting the price tables with the Shopping Cart page

Hi everyone,

I am having trouble connecting the price tables to the shopping cart page. I have been following a tutorial which said that you have to create the products then use the ID numbers to redirect the user once he clicks on the appropriate product on the price table and this will send them to the Shopping Cart page but for some reason this is not working for me and I dont know why.

This is the url I have added to the price tables:

https://websitename.com/?add-to-cart=251

But it is not taking me to any page on the website when I click the buy button on the price table for this product.

Many thanks.