1) To start, open the "Reports" dropdown inside the dashboard on the left of your screen. You can choose any report; the screenshot below shows the Item Sales as an example.
2) Inside your desired report, you can see a date range above the table next to the "Download" button. Click on this to edit the days you want to see and export.
3) Now you have selected your date range, you can click on the "Download" dropdown button and choose your preferred export.
4) All done! Your export should start downloading.