During load time, the tutorial is displayed. Once Xcas is ready (this will take more than one minute the first time, at most a few seconds the next times), the tutorial will be hidden. You can display it again by clicking on the Tutorial button.

Command :               
A typical Xcas session will consist in entering commandlines that will appear in the history. Sometimes you will also edit an already entered command and reevaluate it.
The screen is divided in Examples of input: