I hope someone can help me. I'm new at this, and very impressed.
I have a shot where a light source travels from right to left across
the screen. The background is a bmp picture. What I need is, as
the light source moves across the screen, I set up a lens light flare
effect, but I want it to vary in intensity (Transparency). Minimum at
the beginning and end of the effect, and maximum at screen
position 360 (directly infront of the camera.) I manually generated
the light circles, but I cannot vary the transparency or manually
place any keyframes inbetween the start-stop of the effects shot.
What am I doing wrong, and is there an easy way to do this?

You want to apply the "Transparency" grading object to the lenseflare effect/footage.

Then you can keyframe wherever you want the transparency to alter.

Thank You

In this case, you are able to alter the optics entire transparency from within the optic itself, as the optics engine has its own transparency controls built into it. To do this, select "Optic movement", then alter the optics transparency as desired, from the "Effects Inspector", located on the right.

You are also able to alter the opacity of each individual shape of the optic, for even greater control over the effects transparency. You may find using the included transparency controls of the optics engine will provide you with better results then using a grading filter, as a grading filter tends to make the effect look more "dull", due to how it is applied to the object.

Take care.
Wizard.