Here's a step-by-step process to tune your guitar half step down:

1. Start with the sixth (lowest) string. Tune it down a half step to Eb. Remember, it should sound a half-step lower than the standard E note.
2. Next, move to the fifth string. Lower it a half step to Ab.
3. Continue this process with each string until you’ve tuned them all down a half step.

You can use a chromatic tuner or tuning app to tune your guitar half step down. There are many free and paid tuning apps available for smartphones and tablets that work in a similar way to a chromatic tuner. You can also use a capo (guitar clamp) on the first fret, tune the strings to E, A, D, G, B, E, and remove the capo. The open strings will now be a half step lower than usual.