You can do call monitoring to gather stats, observe average call time, and more helpful tools within your 3CX web console. There are two main tools that are needed - a Switchboard and a Wallboard. First, Login to the 3CX Web Console (Instructions came in your welcome email). Then, here's how you access them:
Switchboard
Click on "People" on the left. It will display a switchboard of all company extensions, who's on or off the phone, and more. It will look like this:
Wallboard
Login to the 3CX Web Console (Instructions came in your welcome email)
On the left, select "Switchboard"
Then, select "Wallboard" on the next menu.
This will display the information you need to monitor calls, as shown below.