Go to your Shopify Admin Portal  > Online store> Theme > Action> Edit code. Search for the exact liquid-file which contains of your collection page. Once you have located the page, go to the link here and copy the snippet for the button icon. Place the copied snippet next to the desirable position on your collection page. 

(Example, if you wish for the icon to appear next to the price, place the snippet after that respective line of code.)
Hit “Save” and clear the cache and cookies to view your changes on the live page.

NOTE: Code snippet must be placed outside of the condition-block. If misplaced, the icon might fail to appear on certain conditions