How to add custom fields to the shopping cart when clicking on the "Order" button?

Question

PHP

Good afternoon! I am making an online store on bitirx version 16.5.4 and faced the problem of adding product characteristics to the cart.
I have a product without a trade offer, of the "simple" type, and it has characteristics that need to be transferred to the cart and to the order. .
In the client part, in the default template, it looks like this:
I specify the "Shoe size" Product Feature in the component settings and when I click on the "Add to Cart" button, a popup window pops up with the size selection.
Actually at this stage, the question arises:
How to implement the addition of goods to the basket and to the order with the selected size and current article so that there is no pop-up window? And the sizes were chosen in the card or on the spreader, as in the image
Tell me please.