Use mask in image editor and compositing for video

Hello everyone,
I’m new to all this. I found a YouTube video in which explains how to change eye colour in compositing and using image editor for a MP4 video.

When I select the eye for the mask and go back to compositing to connect everything, the white mask doesn’t show up, and when I go further to change the colour of the eye. My eye colour stays the same.
What step did I forgot to take? Does anyone has other tips?

Oh and how can I make under my eyes red? How can I make some kind of fluid get out of my eyes?

Thanks in advance for your time.