For a community site, you’ll want to make the home page a static page. To do this, first create a home page. Also create a news page. Then in Appearance -> Customize, Pick the “Static Front Page” menu and set your pages. If your theme doesn’t support Static Front Page, pick a different theme!
Once you pick a theme, you can customize it. Most themes let you set background colors and images, set a header image, etc. A Link!
Try changing your theme. Find a cool new theme and ask the teacher to install it. Themes are under the “Appearance” menu in the Dashboard.