Select “Check Design Rules” and double click.

Screen after double clicking on “Check Design Rules”

Select Launch ModelSim

The screen after double clicking on Launch ModelSim

Assign values to the input signals. Select signal ‘a’ on the “signal” pop up and click edit.You can “force” the signal to 1 or 0, or choose clock and choose a period of 1000 for example.Do the same for signal ‘b’ and select 2000 for the period.

Assign value for signal b, select a clock with a period of 2000 (doublethe period of ‘a’.

Waveforms after clicking “run” on the waveform pop-up.