Hi Tania - looks like your About Us links are leading to a 404 page right now. Do you have a page called "About Us" or something similar in the Online Store>Pages section of your admin? If not, you'll need to create it first, and then take note of the page's title.
You can then link 'About Us' in your store's main and footer menus to this page by popping into your Online Store>Navigation and editing the menus so 'About Us' points at the page you just found/created. It should look something like this:
Let me know if that doesn't answer your question and I'll have another go :]
You'll be able to find the "about us" page in the pages from online store/pages section. If you don't have one set up, create one by adding a page from the "add page" button to create the about us as a page template.
You can refer to the Shopify tutorial to make pages.
Hope that helps,
Issue fixed so going next, you might consider to take a look About Us page examples blog post about how well made About Us page affect on the online store conversion rate.
Tony - reviving a thread from over a year ago to post about your app isn't cool.
Add to that I can see a pile of posts from you and others from sellersmith - often on the one thread. It's getting to the point that they'll likely get flagged for spam. Please don't spam the forums about your app - this is not the venue to advertise.
Closing this thread.