Connect the RCA output from the turntable to the the "phono" RCA input on the left side of the mixer. Make sure to connect the leads to the same mixer channel. Unscrew the cap from the grounding post on the same channel where you connected the RCA cable. Hook the ground wire from the back of the turntable to the post and tighten the cap to hold it in place.
Connect the mini end of the mini-to-RCA cable to the headphone jack on your laptop. Connect the RCA end of the mini-to-RCA cable to the RCA input on the right side of the mixer.
Connect the master output from the back on the mixer to your speakers and plug your headphones into the headphone output jack. Drag the vertical level faders all the way down to zero.
Place a record on the turntable and select the appropriate speed. For seven-inch records, select 45 RPM. For 10- or 12-inch records, select 33 RPM. Start the turntable and place the needle onto the record. Drag the cross-fader all the way to the left to send the output from the turntable to the speakers. Slowly lift the vertical fader on the left side of the mixer until you can hear the song playing on the record.
Launch iTunes and double-click on a song title to begin playing it. Slide the cross-fader on the mixer all the way to the right to mute the turntable and send the output from iTunes to the speakers. Slowly lift the fader on the right side of the mixer until you can hear the song playing in iTunes. Practice sliding the cross-fader back and forth between the two sources until you can perform a smooth and continuous cross-fade.