At the start of the day you’ll open your shop with a float in the till so that you have enough to give customers change. Whatever the amount you choose to put in at the start of the day you can record using the Cash in button. This won’t create any accounting, but simply prints a receipt for you to place inside the till so you know how much you started with and therefore can work out how much you’ve made over the course of the day.
You may also choose to remove cash from the till throughout the working day. This might be because there’s a lot of money in there and you’d rather store it somewhere safer, or because you took some to buy milk for the staff tea room. Whatever you take out you can record using the Cash out button. This won’t create any accounting but will print a receipt for you to put inside the till so that you know who and how much was taken out and can therefore make sure your takings tally up with the sales for the day.