In the top right corner, you will find the settings. Here you can change various preferences, such as your avatar or microphone. You can also log out here.
With this setting, it is possible to pick up less ambient noise. This way, you will have less of an echo.
Set the Microphone Activation Sensitivity to 1 or 2. You do this by moving the white square on the slider. Click on the white bar and move it to the left.