Hi , in top of the page , next to inbox , or “消息中心” if you are the page in Chinese; next to it you see a small circle , its for chat and you can choose to off on on the chat. Hope it helps !

To chat, you can either submit a question (just like this one) and have people comment or for instant messaging you can use the "talk bubble" at the top right of the screen next to your "Inbox" and "ITC points".

on the lower-right-hand side panel, click on the button "groups", then choose a group to join for chat.