You must specify the general conditions and your priorities for the timetable before you can start automatic scheduling. This is done in the relevant window which can be accessed via the 'Weighting' button.
The Getting Started Weighting can be found here.
The Getting Started Optimisation strategies can be found here.
The Getting Started Evaluating timetables can be found here.
The Getting Started Timetable diagnosis can be found here.
The Getting Started Lunch break can be found here.