Make sure you have the latest version of Google Chrome installed on your desktop, or download and install it here.
Add the Whilo extension from the Chrome Web Store here.
You should now see the Whilo icon to the right of your URL/Address bar in Chrome, navigate to any product page you wish to add and hit this button.
The widget will do it's best to find the information it needs on the page, but you can complete the Title, Brand, Price, Category etc to correct it or fill in the blanks.
NB: If you're viewing this from your mobile device, the Chrome Web Store link above will give you the option to send a reminder with the download link to your desktop machine.