Redirect cart icon link to external page

I am trying to change the link the cart button leads to. 

For background, I am trying to mimic the navigation bar from my Square site (https://dishedbyrachel.square.site/s/shop) on my Squarespace site (dishedbyrachel.com). Ultimately, I want all of my site content to be built/hosted on Squarespace except for the storefront, I want to utilize Square's storefront page as I already have it set up for the business.

I figured out how to customize the cart icon to match Square's, but when the cart icon is clicked, I want it to link to https://dishedbyrachel.square.site/s/cart.

Alternatively, if this isn't possible, if there is a way to just add a custom icon to my nav bar (preferably to the right of my Order Now button), that would be great.

but when the cart icon is clicked, I want it to link to https://dishedbyrachel.square.site/s/cart.

I see you figured it out?