I accidentally delete or replace very important note

Like I said: I lost my note by deleting or replacing and I read on some blog that I can restore it by doing the backup from i-tunes. So I checked my itunes and find out that was last time I back up on this computer was done 4 months ago. At that time note was existing. I done care for rest of the file I might lost but how can I resore my phone from that point. I would really appreciate if we can simple step explain me how to do.

Thanks in advance!