There are two ways to manually open a report: from the Home Screen or from Report Mode. You set the default folder for reports in the Report Options.
Under the Reports header, select Open an existing report. The right side of the screen will be divided into two sections. From the top section you can select your most recent report. The bottom section lists reports you've opened or created in the past. If you don't see the report you're looking for, click on the more files... selection in the bottom section.
Click on the Open Button in the Desktop Toolbar, or select Report | Open | Report. You can also select a recently-opened report from the list at the bottom of the Report menu.