To add / update the website listed on your businesses page you must first log in as the business owner. If you do not have access, How do I claim my business profile? will show you how to claim the business page.
1. After logging in to the Business Center, scroll down to the Your Nominee Page section and click on the "Manage Your Profile" link:
2. Next you will need to scroll down to "Links to other networks" and input your website's URL and hit save
* Please note: In order for your Twitter and Facebook accounts to appear on your public profile you will need to add them in their allotted fields as seen in the screenshot above