music score octave

Hello;)
I am trying to move MusicScore piece by Rachmaninov 1 (one) octave down to be able to play the music on a Cello. The original piece was created for Violin and it is G5 first note. I need to bring it down to G4, as well as the rest of the notes in the composition. I spent about 30 minutes trying to do that, to no avail.
Any help would be greatly appreciated.