From the Task Bar at the bottom of the screen, touch the Control icon.
Touch the Intensity icon to access the Intensity tool bar and various tools.
Wheels: Use the green wheel to set a level as a percentage.
Libraries: Select from standard intensity levels.
IRGB: Use the on-screen faders to adjust intensity and RGB values. (Applicable only if you light has color mixing attributes.)
Effect: See How to Set an Effect