How do I change a serpentine belt in 1997 nissan?

some have a place that looks like the end of a racthet to fit in that you can pull one way or the other on or around your tension pulley but they will be one of some sort there even if you have to loosen one of the things it turns it is usally fairly simple and fast but pay att.to the way it comes off so it dont confuse you on replacing it