I feel pathetic posting this.

My fiance just introduced me to the idea of submitting my work to "stock" sites.
I'd like to give this a try and I have no clue where to start.

Any suggestions of what site I should use since I'm a novice when it comes to submitting stock? I mainly have nature/animal photos and obtaining a model release (some of my work is of my best friend) would be effortless (if I just knew what exactly I need to do).

Thanks in advance.