Screenshots, exact effects settings, comp settings, system specs. Going without any of this info would be pointless guesswork.
Are you looking at the LAYER window or the COMP window? It sounds like it might be the layer window.
It also sounds like you should spend some quality time here:
With AE, you can't blow off the basics. If you do, you'll get lost. If you're familar with other software, you'll progress quickly.
My pointless guess is that your footage is mostly light, maybe even white. White + white for the snow effect = white so you can't see anything. A screen grab of a single frame would tell us a lot. A screen grab of your composition revealing all properties that you have changed would be better.
Try creating a new black layer, applying the effects to that, and setting the blend mode to screen to remove the black