How to change my aspect ratio to 1:1 for my shop?

Here is the link to what I'm talking about: https://www.bjcartanddesign.com/shop/custom-digital-art

As you can see when you click on the link, the art is too zoomed in at the current aspect ratio. I would like it to be the 1:1 ratio. 

Is there a way in the squarespace settings to where you can set up different aspect ratios per product or is it all with coding?

Thanks!

Try adding this to Design > Custom CSS

.products.collection-content-wrapper .grid-item .grid-image-cover {
    object-fit: contain !important;
}