The About page has a special "Page Options" module where you can include a sub-group of the People section on the page. This is where you can control what sub-groups you may have created in the People section of the site to appear on your About page. Your site comes pre-loaded with a "Leaders" sub-group. As you add additional chapter members into the People section, you can add them to a sub-group and as long as that group is checked on the About page, it will appear on the site.
Here's a view of an About Page before and after the "Athletic" sub-group is checked to appear on the page: