How do I remove a section that I don't want to use?

You can remove a page from your website's layout by clicking on the page's tab in your editor menu, and then clicking the grey "Remove this page" button at the top. 

If you'd like to put it back, just click on the "Add/Arrange Pages" tab in your editor menu, and scroll down in the editor window to the "Add Pages" section. Click the "Add..." button for the page you'd like to add back to your site.