To track overall chat metrics (or those specific to an individual agent) go to the Reports section in the left sidebar and select the Team Members report.
On the top right, select a time period and pick an agent from the dropdown list. 

You can then see the numbers for Total, New, and Closed conversations for the selected timeframe by clicking on each category, as well as average first response, assigned first response, and chat closing times.

• FRT (First response time) - is measured from the time the customer initiates a new chat until the support agent sends the first message in that chat. Less is always better.
• AFRT (Assigned First response time) - is measured from the moment chat is assigned by auto-assignment rules or by a chatbot rule, till the very first message from the agent. 
  AFPT can be "0" if support agents assign chat to themselves by answering it, if it wasn't assigned to them automatically.
• TTC (time to close) average conversation duration time. In this case, the less is better, but mind that it fully depends on whether you are closing conversations by changing their status to "Closed".

Median values

Export numbers to xls or csv

The report figures are interactive. To explore further, you can click for example on the "Total chats" number, which will allow you to view the chat list and export it as an XLS or CSV file using the three-dot menu at the top. 
You will receive an email with the file shortly after.

See also: Customer satisfaction report