How to open the film door on my Nikon FM2?

I just inherited my mom's old fm2 because I told her I wanted to take up film photography. I went to take the film out and the door won't open. I think I might be doing it wrong, although it seems like it's just jammed. I'm holding the release lever down but it won't open.
Could you give me step by step instructions? If it happens to be jammed, how would I open it?

Generally, Nikon film doors are opened by pulling up on the rewind knob. The button on the bottom is to release the take up reel when rewinding the film. I would suggest downloading the manual for this camera. There are a number of web sites with scans of camera manuals in PDF.

Talking to mom about operating the camera might be a good idea.

Look at the rewind knob on the top left side of the camera (opposite side of the wind lever). HOPEFULLY, after pressing the release button at the bottom, you rewound the film back into the 35mm film canister, or else you'll ruin all the pictures.

Now, you'll see a little lever at the base of the knob. Slice it to the side, and it will allow you to pull up on the rewind knob. When you do that the back door will pop open. It works exactly like my FM and FE.

Here is the user manual which will have all you need to operate your fine camera

http://www.butkus.org/chinon/nikon/nikon_fm2/nikon_fm2.htm