Make text area into fixed footer

Im using formcraft and love it but have run into a little problem with css latley. I want to make the class .cart which is actually a text-area field inside a formcraft form to be fixed at the bottom the the screen at all times like a fixed footer. Currently user has to scroll all the way to the bottom of the page to view this div. I have tried the following css but to now avail.

I have highlighted the div .cart with yellow color on the page.

My webpage — > https://omgjewelz.com/create-your-set

I have currently tried this css but it does not work.

.cart { position: fixed;
    left: 0;
    bottom: 0;
    width: 100%;  } 

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