Crysis Sandbox trouble

[spartan0078]

So i just installed crysis 1 to play with the sandbox, something ive never done and have no esperience in, all i want to do is play aorund like the youtube videos of ppls tacking barrels and blowing them up etc etc etc... But everytime i place an object it jsut floats in the air and i cant interact with it at all even when i press Ctrl-G to go ingame the barrels just continue to float and not let me do anyhitng to them at all, anyone help me at all?