You can use the I/O panel to change input states (analogue and digital) and monitor outputs (analog and digital). All the symbols/addresses from the table of symbols are displayed. You can use the buttons at the bottom of the window to define which areas should be displayed.
Changing inputs only makes sense if the simulator mode is active and if no virtual model is used. Otherwise, the inputs are immediately overwritten.
From a certain number of inputs and outputs on, it makes more sense to use a virtual system/machine for the simulation. The big advantage: The inputs are automatically written via the machine's sensors.