As discussed before, things aren't vary clear.
I remember when I joined up, I had the same problem.
When I read "add note" I thought it meant add a note or post to the forums. I think being right in the middle of the starting page, Sandwiched between "home" & "forums" was part of the problem. The other problem being that 95% of people that I know call them BILLs not notes.
I see people sign in daily, create a user name & then don't enter a BILL. I usualy PM them the folowing

("Hi, if you found a marked note (a bill with this website stamped or written on it)
you need to click on the "add Note" button or tab & enter the bills serial # .
Three letters first, then 7 #s.
Then you will see the history of your bill.
Its fun to see where you money has been.
Make sure you enter all marked bills you come across!
Any questions just "Private Message" me.
Have fun tracking.")

Often times these people come back on & enter their bill!, thanking me & stating they where confused.

Mike Cityscape