In order to use swift with Audio for VATSIM, you will need at least a Beta version of swift. However, until further notice we recommend using alpha versions (Other Downloads). swift's Alpha versions are stable, don't worry!
The first time you run swift, select the Audio widget and then the Devices and volume tab. Choose your input and output devices and calibrate your microphone. When talking, the bar should be bouncing into the green band. If it does not, increase or decrease the mic volume using the slider.
If not done during installation, assign a push to talk key in swift's GUI Hotkeys settings.