If you would like to connect with your friend on the Status app, you would need their chat key to send them a message. Click the + button, then Start a chat, then enter your friend’s chat key and kaboom you find them.
To get your chat key, head over to profile then click the button on the top right most corner, from there you can copy your chat key.
It is also possible to message anyone if they are participating in a public chat, all you have to do is tap their avatars and you can send them a message.