Can I play tracks from iTunes or YouTube?

Yes.
Set the [MIXER MODE] on the XDJ-RX3 to [XDJ-RX3] in the Utility settings.
Audio comes into channel 1. Turn on Control mode on DECK 1.
To turn on Control mode, see [Using DJ software] in the Operating Instructions.
You can read the Operating Instructions [here].

You can adjust the volume with the MASTER LEVEL knob. When listening with headphones, turn on the MASTER CUE, turn the HEADPHONES MIX knob all the way to the right, and adjust the volume level with the HEADPHONES LEVEL knob.

Some files, such as Apple Music tracks, can only be played with certain players so you may not be able to play tracks like these. Depending on the situation, you may have to change the audio setting on your PC/Mac. You can change the setting as follows:

■ Windows
Click the speaker icon in the lower-right corner of the screen, then click [Speaker] to switch to [Line XDJ-RX3].

■ Mac
Open [System Preferences] -> [Sound] -> [Output] -> [Sound Output Device] and select [XDJ/-RX3] as the sound device.