The mouse can be used to select fixtures and set levels.
Before
selecting a fixture it will look like this: 
(may be magenta,
blue or green)
Left
click the Mouse on the Fixture Grid to
select a fixture. It should look like this: 
Hold the left button down and drag across the Fixture Grid to select several adjoining fixtures.
Touch fixtures again to de-select them.
Note:
Even if a fixture is selected, running cue lists can still alter its level until you capture it.
You can also select moving lights with the mouse by touching them in the Attribute Grid.
Select a fixture as described above.
Roll
the wheel in the middle of the mouse
(or the wheel on the console). The level changes in the same direction
you roll the wheel. The fixture will get a white triangle (delta symbol)
showing the changes to be recorded. It will look like this: 
Each detent (or bump) on the wheel will adjust the level by 1%. Holding down [SHIFT] while rolling the wheel will give you finer control.
Note:
If you then go and select other fixtures, the previous
fixture will look like this: 
The fixture is still Captured
and has changes that need to be recorded. Running Cue Lists or Look Masters
cannot affect this fixture until you release
it (unless you are using Last Action Editing as determined by settings
in Hardware Setup - Console)
You may also want to purchase ELO Touch Screens for your console as selecting fixtures just as easy using your finger.
See Also:
Selecting and Setting Fixtures