Nikon d5100 RAW/image overlay/multiple exposure

I got my NIkon d5100 about a year ago and I need a few suggesting. I have been trying to figure out how to convert my pictures to RAW to follow through for image overlay. It will not let me and it says "no image for retouching". Also when I want to do multiple exposure, it says "this option not available at current settings or in the camera's current state." I have tried putting it in every setting.

You have to shoot in RAW in the camera.

RAW has all the data collected by the cameras sensor and it remains unprocessed until you copy them to your computer and then process then one at a time in Photoshop or in mass using Lightroom

After you process them, you can export the as either JPEG or TIFF files to your computer

What you are suggesting is trying to put that cake mix back into its container after you have baked the cake

RAW files never change. Any changed you made in Lightroom will be saved with a companion XMP file that keeps track of any changes you made while processing the original RAW file.

You have to shoot in RAW to do image overlay.

Read Pages 47-48 in the user manual to put camera in RAW.

Read Pages 78-80 in the user manual for multiple exposure.