Link to open the cart

Hi, in this post you mention that to open the cart via a link we must add a class and place it in the settings area.

https://wordpress.org/support/topic/link-to-open-the-side-cart/

I’ve checked on the advanced section but there is not area to input the newly made class. https://prnt.sc/u0KfmHRGYt_J

How do i add the class?

Thanks