The Mr Coffee web site has the manual on the product page: http://www.mrcoffee.com/coffee-makers/mr.-coffee-optimal-brew-10-cup-thermal-coffeemaker-black/BVMC-PSTX91.html
. Click on the Service and Support tab. The direct link to the manual is http://demandware.edgesuite.net/aamb_prd/on/demandware.static/Sites-mr-coffee-Site/Sites-mr-coffee-Library/default/v1426159971356/documents/instruction-manuals/BVMC-PSTX91_43_72624326.PDF
. (You'll need Adobe Reader or a similar program to print the manual.)
The Clean light will come on when the Clean button is held. It won't go off until the cleaning cycle is complete; it's completely automated. You need 4 cups (20 oz.) of white vinegar or the Mr. Coffee Cleaner (diluted as directed on the package). Make sure to remove the water filter disk from the unit before cleaning. Pour the vinegar or cleaning solution into the reservoir into the reservoir. Put in a paper coffee filter or the permanent filter into the brew basket and slide it into place. Put the empty decanter in place. Now you should press the Clean button until the Clean light comes on. The unit should slow brew 3 cups of the cleaning solution and then pause for about 30 minutes while the Clean light remains on. It should then brew the remaining solution. After the cycle finishes, the Clean light should go off. Afterwards, you need to empty the decanter and rinse it with clean water. Fill the reservoir with fresh, clean water. Then replace the decanter. The cycle could take an hour.
I hope this helps.
(some brewing systems light the Clean lamp when it's time to clean the unit after lime deposits build up. To my knowledge, most of the Mr. Coffee brewers do not.)