Each report and subreport is opened in its own tab in Report Designer, much like in modern Web browsers and text editors. The currently selected report's tab will always be highlighted in blue, as shown in the graphic below. Click the X in the corner of a tab to close the open report it represents, or right-click the tab to see a context menu that offers more advanced close operations.
The button bar below the tab area offers font and preview options. The eye icon switches to preview mode, which shows you approximately how the report, as currently arranged, will display when published. When you are in preview mode, the eye turns into a pencil icon; click it to return to design mode.
The rest of the functions in this bar are standard font controls found in most text editors and word processors. The list of font types is pulled from your Java Runtime Environment's fonts directory and from the TrueType fonts registered with your operating system or desktop environment.