How to add effect to specific area of video?

Hello,

I'm trying to add an effect (glow) to a specific area i've masked but every time I try to do so the effect applies to the whole video and not just the selected masked areas. Is there a way I can make the effect only happen on the selected masked areas? I'll provide pictures below:

This is the image i'm trying to add the effect to. As you can see i've masked the eyes and added a yellow fill. I want to make this area glow, however:

Whenever I add the effect it adds it to the whole composition instead of just the eyes.

Is there any way to fix this? I'm a beginner by the way