Anything blue opens something. Each tile names its page in the corner (Sales ›), pill buttons open pages, and ← Summary takes you back.
To see the rows behind a number, click its bar, point or row. The grey Invoices › or Customer › button over that chart turns blue; click it.
Hover a customer for its last 12 months.
To start over, click Reset at the top of the page: every page goes back to the way it opens. It turns solid blue once you've clicked something. To undo just one click, click the same bar again, or an empty part of that chart.
Full screen: the corner button next to ? (Esc to leave).