You can already chat on the concert's page, if you have logged in to LiveYu. You're Facebook or Google profile picture is also displayed on the chat, if you logged in those social accounts. The chat contains the standard features: you can write messages, send emojis and gifs. Your message can be sent with the large purple 'Send' button. You can also like other users' comments, or reply to the with inline buttons.
You can hide the chat with the arrow found next to it's top left corner, and you can unhide it with the same.