Another way to start a convo on P.M. (private messages) is by the message board sign, there would be something else that says 'Send Private Message' to 'Send Message', and you would press that to start a private message.
Normally, though, you would have to go to the place where it says, 'Hi (insert username here)' Don't press on it, just put your mouse there. Look lower and below 'Profile' there would be 'Private Messages', usually.
mkay... so this is for private messaging. go all the way up. You see that watt pad logo and the black bar underneath it? The one that says ' What's hot What's New Discover' etc. etc.go to the right and there will probably already be something there that says 1 or 2. Press that, and you'll get to the private messages. This only works when you've got mail