You go the line/location/chapter you want to note, click down on your scroll wheel...give it a couple of seconds and a the cursor will move towards the top and the options: lookup, add highlight, and add note will appear. go to add note and click. then input what ever info you to there. Then you should be able to assess it at 'my clippings' or you can click at menu at the bottom of the screen there click on 'my notes and marks'
I think someone else can describe this process better than me.
Adding notes at these locations of the Kindle User Guide:
131, 135, 136, 553, 568, 621, and 623