Your users can access the 'About' page from the hamburger menu at the top left. You can make the About page the app's initial launch page as described here.
You can customize the 'About' page on the Info > Properties tab. You can specify:
About URL. You can enter a URL value in the URL field that provides more information about your application or your company, such as http:\\www.mycompany.com\moreinformation.
For example, here's the About page for one of our sample apps: