I am definitely not a computer xD To
PM(private message) someone, click on their username. A drop down list will appear, second down on the list is a button that say's "Send a Private Message". Or from a user's profile, right under their profile picture, is a button that says "Send message". An even easier way, is go to your inbox, hit compose a message, and just type in their username. To search for a person, for their posts anyway, click the search button, click advance search, and then in the column that says "Search by username" just type in their username, and hit enter.
I hope that answers your questions. If not,let me know, and I'll try to explain it better.~Casey