New to shaders: how can I make an image effect shader that warps the view depending on the texture?

I'm trying to setup an image effect shader that warps the camera view by distorting the surroundings and zooming in and out on a sin wave, I have no idea how to achieve this though; all i've managed to do was make the texture render onto the screen, everything else i've tried just resulted in a bunch of compiling errors. I'd really appreciate it if I could get some help with the shader effect i'm trying to make.