Basically that's it Nora,
the mushrooms need to be FRESH- picked from the "wilds" of your local lawn
or cow pasture.
I'm not sure but the grocery store kind won't do.
The spores drop on the paper overnight and a very neat pattern is left.
A large jar or bell jar make the best covers .
I've had them last in my example file for years.
You can spray them with fixative -just don't spray them too close or hard.
Kids are facinated with the process. Have fun.