Plug your DJ mixer into your computer. If it has a USB input, use that. Otherwise use the line out. You may need a jack adapter for this, depending on your equipment.
Open your recording software, and assign your turntable set-up to a new track.
Apply Auto-Tune to the track. The way you apply plug-in effects to a given track varies depending on the program you're using. In Logic, open one of the blank "Insert" buttons in the window to the left of the track that you want to Auto-Tune, and select Antares Auto-Tune. In GarageBand, open the Track Info window to the right of your track, and scroll through the effects options at the bottom until you find Auto-Tune. In Ableton, drag Auto-Tune from the Plug-in devices window into your Effects chain.
Experiment first with scratching using a consistent tone or with an a cappella vocal track. When you scratch or change the speed of the record, the sound will automatically be adjusted to the nearest preferred tone. Try to set Auto-Tune so that it snaps the notes to the scale of the song that you are playing or recording.