The header cart and my account icons will be displayed automatically after you activate the WooCommerce plugin.
You must setup the pages in the WooCommerce settings. Docs: https://docs.woocommerce.com/document/woocommerce-pages/
Default display (desktop)
By default the my account and cart icons are displayed in the header
On page scroll
When you scroll down, the cart and my account icons floats on the right with the scrolling page.
On the mobile devices is the cart and my account link displayed in the menu bar