Anchors

Hi, I am new to the forum and relatively new to Flash and have come across a problem while following a tutorial online. The instruction is:

*We will create a gradient fill that fades in and out to emulate the flicker effect, go Window>Color Mixer or press Shift+F9 to show the color mixing panel. Set the gradient type to Radial, and create three anchors on the color bar as shown below in the screenshot.
*

I am having trouble with the anchoring part as I am not sure what it means exactly, I have looked on some flash help sites with no solution so it would be great if someone could assist me.

Thanks