The answer to this question depends somewhat on the age of the child.  I am assuming this is a young-ish child who has not yet inculcated the practices in the environment.  When giving a presentation, involve the child in the returning of the materials to the shelf.  You can ask: “Which part would you like to carry?”  Or “Which part do you want to return first?”  When you observe a child who has left material out (if the child is not already engaged in another piece of work), simply say to them, “Oh, I see you left your work out.  That needs to be put away so someone else can use it.”  DO NOT interrupt the child if he/she is concentrating on another piece of work.  Simply put the work away and observe when the child next leaves work out and remind them that it must be returned to the shelf.

If you see a child wandering around, having left work out, simply say to them, “Before some other work is chosen, you must return this work to the shelf so someone else can use it.”  

Try not to engage in power struggles but, at the same time, be clear about the rules in the environment.  Do not say, “I need you to put your work away.”  OR “You need to put your work away.”  Simply state that the work needs to be put away.