Thankfully, tuning a half step down is a very simple process. All you need to do is tune each string down a semitone. So instead of tuning to E/A/D/G/B/E, you would tune to Eb/Ab/Db/Gb/Bb/Eb. Since the flat of one note is the same as the sharp of the note before it, you may see this written as D#/G#/C#/F#/A#/D#.