Is there a way to "pose" a mannequin?

I am making 4 different classes that the play can choose from. Since this is going to be my first game, I plan to stick with the default 3rd person model and just change the material. Is there a way i can pose the character and have it stay in that position, like a statue? I tried the mannequin but I can’t figure out how to move the bones, its just stuck in the default standing pose.