How to do a blinking light animation?

Hello everybody,
I would like to do a blinking light animation, but I cannot figure out how. I can render a nice looking light with halo, but I cannot make it turn on and off in an animation.
Is there a tutorial available for this or can somebody tell me how?
Many thanks
Reiner

In the light settings panel on the frame just before the light flashes off, press I (insert keyframe) and select ‘Energy’. Then, in the next frame, put the energy right down to zero and insert an energy keyframe again. For the light going back on again, just do the opposite.

That´s great!! But how do I manipulate those frames?

With the Arrow Keys on the keyboard or in the framecounter in the Buttons Window’s header bar with the mouse cursor or numerical input.

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