Help with keys and tunings

Hello guys, im a noob at this....For example i have a saxophone *with is tuning ) and my piece is in C major..how can i make to see the saxophone as it was like a flute?(C major armor,without the # # # notes in the key becouse of the tuning) I dont even know how to ask the question..and i see people that make that in their scores and i cant figutre it out..

look in the left and right score for the clarinet and trumpet for example ..the right one says Bb Trumpet but it isnt actually written for that tuning..