WooCommerce is now the most popular eCommerce plugin on the web. Please install and activate WooCommerce plugin to create your online shop.
How to start with WooCommerce(installation, creating products, and so on)? Read WooCommerce official DOC.
Set layout by Appearance > Customize > WooCommerce
Set product thumbnail:
Set products per row on the default archive page(1-6 supported):
The WooCommerce would automatically create a page named “Shop – Shop Page”, it could not be edited by BM Content Builder and page options of Art theme. It is the default page of WooCommerce. You could create a new page to customize the layout for your shop page.