You can search by name ... at the top of your profile page are a couple of name fields (first and last) put in the name and 'Enter' or click on the magnifying glass. If you get too many hits then you can enter some more data at the bottom of that results page ... birth year, etc.
Once you've found their profile there are a couple of ways to send notes ... put a public note on that page ... it's over on the right and down a bit ... or you can click on the 'Send Private Message' link that's in the yellow/orange section ...
