i am using creo parametric 3.i trying to cut the model in the left hand side using the blue semi-circular surface in order to bring it in the exact same form as the shape in the right hand side but i cant.how do i cut using surfaces instead of sketch

hello and thank you for your answer.i do know that but in order to do what you said i have to sketch on the drawing.but i dont want that.what i want is to use the blue surface as a sketch in order to cut it.but i dont know how to do it.i have to use references this won't help me