The Arppegiator on the Deepmind can simply be enabled by pressing the ON/OFF button to enable. The Arp can be set to hold by pressing the TAP/HOLD button for a second. Any sequence of chords will then be arpeggiated. There are a few internal parameters that can control the nature of the arpeggiator:

TAP TEMPO: Tap the TAP/HOLD button 5 times and your arp will adjust to your inputted tempo

RATE: Will manually adjust the rate of the arpeggiators BPM.

GATE LENGTH: Adjusts the decay on the arpeggiated notes. 

Even more parameters can be controlled on the EDIT menu in the ARP/SEQ section:

KEY-SYNC: The Arpeggiator will trigger as soon as a key is pressed.

OCT: Refers to OCTAVE, and allows you to set the number of octaves the arpeggiator runs over.

MODE: Selects the style of arpeggiator, whether UP, DOWN, UP-DOWN, DOWN-UP etc.

HOLD: Sets the arpeggiator to Hold or Momentary. 

CLOCK DIVIDER: Will set the amount of beats played when synced to a MIDI Clock.

RATE: Allows you to set the BPM

SWING: Allows you to apply Swing to your patterns

PATTERN: Allows you to store your settings as a preset. There are 32 Presets here.