You would use get_pages function or create custom query using WP_Query class. The codex pages have detailed descriptions of parameters for both functions.
If this is a theme that you want to release for broader public you would probably want to create a theme options page where user sets the page that he wants to display. If it’s you custom theme where you know the ID of ‘About’ page then you can skip the theme options part and use the page ID in either get_pages or WP_Query method.