Press the Menu button, then tap the MPC chip icon in the top-right section of the display next to the battery icon.
Following this, your MPC will send MIDI data to your computer via USB.
If you haven't already installed the MPC drivers and desktop software on your computer, please do so now by following the support videos linked below; they will walk you through the entire procedure...
Akai Pro MPC Series | Install & Activate MPC 2 Software & Drivers
Akai Pro MPC 2 Software | How to Download, Install & Activate