To begin, access your Google Calendar:
Create a new Event and enter the details of the event. Highlight any sentence or word in your description and then click the link icon:
Enter in a web address here that links to a page on your webstore.
The 'Text to display' section is optional and is if your don't want the highlighted text from the previous step to be the link.
Save, and when you return to your webstore front page, your new calendar event will have a clickable link to a page on your webstore!