half step

See: http://www.martymethod.com/Transposing.htm
HTH

To be fair, the answer is more complicated than that. From G down to F# is indeed a minor second. But from G down to Gb is not - it is an augmented unison. Depending on your reason for doing the transposition in the first place, either of those might be the right choice - or it is also possible neither is correct, and you should actually simply be using the cursor down key to transpose everything down a half step in a way that respects the key (meaning some notes will be transposed down a minor second, others an augmented unison).

-go to instruments and make sure all the parts that you want transcribed are selected as "visible" by checking the box for each part
-highlight all the notes and parts to be transcribed
- press the down arrow key once
waa laa, down half a step...it keeps the same key signature but the sharps or flats are added to the individual notes themselves in terms of the way it looks but it should all sound a half step lower. :)

Sorry this is 2 years later haha

select all the notes you want transposed(click mouse and shift to end) and then just press the arrow key up or down for half steps!