Connect the audio interface to your computer with either a USB or Firewire cable, depending on the make and model of the interface.
Connect a standard instrument cable to each of the out jacks on the rear of the interface. Connect the spare end of each cable to the inputs on the speaker amplifier.
Open your preferred digital audio workstation, such as Pro Tools, Mixcraft or Logic. It may take a few seconds for the program to fully load. Depending on how you have configured your digital audio workstation, either a brand new project or a work in progress opens automatically. If the latter, click "File" and select "New Project" or "Open New," depending on the program.
Click "File" and select "New Audio." This opens a new audio channel. Name the channel "Auto-tune vox."
Click on the channel to highlight it. In the channel strip controls, click on "Settings." Select "Input Devices" from the menu and select an audio interface from the menu.
Click on "Send To" and select "Stereo Master." This configures the channel so any audio coming in from the audio interface is routed to the master output channel.
Sing into the microphone and adjust the "Master Volume" dial to set the volume to a suitable level for your environment.
Click "Effects" and select "Auto-tune." This sets the pitch-correction software to run in the background, grabbing out of tune notes and correcting them.
Set the "Retune Speed" dial to your preference. Set it low for a "stepped" correction sound similar to that used by T Pain. Set it high for a more natural correction.
Set the "Tracking" parameter. The two extremes of this parameter are "Relaxed" and "Choosy." The former corrects only obviously out-of-tune notes, the latter corrects anything that deviates from perfect pitch. Set it somewhere between the two that suits your style. The closer to "Choosy" you are, the more obvious the Auto-tune effect will become.