Connect your MIDI keyboard to your computer using a Universal Serial Bus MIDI interface. Older computers may have a five-pronged MIDI input that connects directly to its sound card, but newer computers connect using a USB port. When using a USB MIDI interface, you need to install the drivers for the USB connection. These are found on a CD-ROM included with the interface.
Open the music notation software program you'll be using to convert your MIDI file. Configure the MIDI connections by choosing "MIDI in" as the source. This tells the computer program where the MIDI files are coming from.
Download the MIDI keyboard file into the music notation program. Depending on the type of software you use and the specifications of the MIDI file, you may see a single voicing or multiple voicings on different staves. You can also put MIDI keyboard inputs into the program one note or chord at a time as you play each on the keyboard.
Edit your completed sheet music file by adding any expressive or interpretive markings and tempo changes and checking for note inaccuracies. Many music notation software programs include a playback feature so that you can hear the finished product and make any necessary changes based on what you hear.