Adding item to card wooCommerce

I want to add an object to cart
I saw a post which says that a url can do that.
it says that https://www.website.com/cart/?add-to-cart=5002 will add it
And seems it’s working but needs some more variables
Page says “Poster Type” and “Poster Size” are required fields

Question: In which file will i can find that what variables are required ?

https://www.ads-software.com/plugins/woocommerce/