Once you've added a GA tag to the admin, you can access advanced stats thanks to the events which are published in GA
Chat usage stats
You can for instance create a widget on your GA dashboard to follow the number of users who uses the chat. To do so, create a new timeline widget.
You can then select the "Users" stat and add a "Event action" = "chat" filter. You will get a timeline of the number of users generating "chat" events (which corresponds to new chat messages).
Here is the list of available events:
category=publication and action=chat : publication of a private chat message
category=publication and action=groupchat : publication of a chat message in a room
category=publication and action=post : publication of a post or an event in a group
category=publication and action=privatepost : publication of a post or an event to a user in private
category=publication and action=privatepostmulti :publication of a post or an event to several users in private
category=publication and action=comment :publication of a comment
category=publication and action=like :like of a post or a comment
category=search and action=group id or all and label=keywords : search query
category=oodrive and action=sharefiles : sharing files using oodrive