Here is a link to a the product page for one standard Whirlpool microwave model currently available:
And here is a direct link to the User's Manual for that microwave oven (model # MT4155):
To view the Product Support Page or the Owner's Manual with Operating Instructions just use your mouse to click on the link, which is the underlined and highlighted text just above. This will open a new web browser page automatically for you and allow you to view the information at the website indicated and the contents of the Owner's Manual.
You may need ADOBE READER installed on your computer to read PDF documents.
You can download this free at WWW.ADOBE.COM
Click on the DOWNLOAD ADOBE READER button on right side of the ADOBE home page when you get there, then follow the onscreen instructions to install the software on your computer.
See page 10 of the manual for detailed instructions on how to use the POPCORN feature in that microwave. Here is an excerp from that section of the manual:
To Use POPCORN:
1. Place popcorn bag on the turntable and close the door.
2. Touch POPCORN once for Regular, or twice for Snack.
Touch START, or wait for the microwave oven to start the
popping cycle automatically.
When the cycle ends, "END" will appear in the display, and
the end-of-cycle tones will sound, followed by reminder
3. Touch OFF or open the door to clear the display and/or stop
I hope that was helpful to you, good luck and take care.