Using Part ISO mode, you can adjust the volume of the selected part (Drums / Vocal / INST) with the EQ (HI, MID, LOW) knobs.

Press the headphones [CUE] button (on the channel) while holding down the [SHIFT] button to switch between EQ mode and Part ISO mode for the EQ knobs on the channels that are controlling DJ software.

For details, refer to the Instruction Manual > [Part names and functions] > [Mixer section] > [9 EQ (HI, MID, LOW) knobs].

You can read the Instruction Manual [here].