m230 fm radio

i turn on my m230 5-8 times a day for a period of 15-20 minutes.  then it is off for 1-2 hr.  how do i get the fm presets to stay?  right now i am only setting 2-3 channels because of the time but would like more choices to be there when i access it.  any help in saving presets for future use would be appreciated.