When you create your meeting for the first time, you are asked to give your meeting a name under the general meeting info section. But if you decide you need to change it, there is always an option of going back and changing it.
To edit a meeting name:
Go to your meetings list by clicking on the black & white house icon top left (from the dashboard) or on the blue meetings tab depending on where you are.
On the meeting you want to change press the 'more options' (or three dots) icon.
Edit the name of the meeting.