If you're talking about animating the intensity then its just as simple as every other attribute that you can right click and "set key". You can even tweak the curve in the graph editor. Anything other than that, you will have to grab that "shader glow" shader that's always there in Hypershade and edit the glow properties on that. Keep in mind though, this is the master glow and will affect any shader with any glow intensity (which can be a good or bad thing). Hope that helped!