On the web, open the message screen to access Attachment and Details option. In mobile, the two options can be accessed in the top right of the message. Attachments displays all the shared attachments. Details will allow you to change the chat message name, add participants and leave the conversation. On web and mobile, users have the option to mute chat.

Chat Message Details in BizChat

Sending Attachments in Chat Messages on BizChat

Chat Settings on BizChat Mobile