Hello Pmedina. You can record VAW but not MP3 on the keyboard.
Just connect a USB stick to your keyboard, go into the recorder and press the red button, then the start/stop when you want the recording to start. For converting to MP3 I use the free program Audacity, with a "plug in" program called lame. Your recording is automatically saved to your USB stick on the keyboard, so just take it to your PC, open Audacity, import the file and convert it to MP3.