How do I review my "Store Preferences" for the Steam Summer Sale Stickers quest?
Your preferences can be accessed from a button on the store's front page.
The "Store Preferences" portion of the text you highlighted is a link, and will take you to the preferences page. Upon visiting it, you'll get the sticker pack.
The more usual method, that will continue working after this sale is over:
And from the web-interface:
