Click on [Start Selling] (the Cash Register icon)
You will see the main Cash Register keyboard, as in the picture on the right.
Suppose you are a Pastry Shop selling cakes, hot drinks, and cold drinks.
You can use Dept 01 for cakes, Dept 02 for hot drinks, and Dept 03 for cold drinks.
I come and buy 3 cakes costing 75.00 in all, and one cold drink costing 15.00.
So you type 75 and press Dept 01
Then you type 15 and press Dept 03
Then you press Go.