When you enter a new item to the database, choose firstly the correct date in the date-picker. As default, the current date is selected whenever the program is started...

...You can now select the corresponding category and sub category for the new item from the respective list-fields. After that, just enter the amount and press "Enter"...

...The table view will automatically switch to the corresponding income- or expense-table and shows the new item along with the others. The Total of all values contained in a table is always shown in the right-hand lower corner.