If you come across someone interesting, you just have to pull up their profile in the app and click on the chat icon. Go for it! You are only one click away from an interesting conversation!
If the chat has been opened, simply write your message and send it. Remember that you only have one chat request per user, so be creative!
By the way: You can book the "top chat" function so that your request is displayed at the top of the incoming messages of your chat partner.