Reduce MB of photos to print (4x6)

The size in megabytes of a photograph has zero bearing on your ability to print it. Can you explain more?

6 x 4 is an aspect ratio. You can print the same image as 6 metres by 4 metres or 6 inches by 4 inches. Can you clarify?

My printer (cannon) says the photo is to large to print

The photo is the image. It's saying the dimensions you have chosen are too big, not the file size. So double check your print settings.