Code Snippet Above Main Image

I’m trying to add a form snippet onto the homepage’s main image. I’m not sure if this is possible and if so, where I would be able to add the code.

I want it to look something like this : http://www.expedia.com or http://www.airbnb.com

thanks in advance.

wp.gridwaste.com this is our site. I want to snippet to be on the left of the red garbage truck.