Click in the "Card code" box and tap the employee's card on the reader — the code fills in by itself.
Fix mistakes here — e.g. someone forgot to press "Work end". Change the times and press Save.
Default PIN is 1234. Change it before putting the tablet in the shop.
All data is saved inside this tablet's browser. Download a backup regularly (e.g. every month) so nothing is lost if the browser data is cleared.