Stage Emitter?

I'm new to this program. How do I find "Mask Emitter with Image" option? I did go online to look for this and some people said the Emitter should be STAGE not LIBRARY. So I did some changes to a Library Emitter. I wonder how I could save it as a Stage emitter so I can use it with "Mask Emitter with Image".
Is there any tutorial about making Stage Emitter or something?
Please help, Thank you!