Just find a toilet with a turd in it, and press "X" (on Xbox) when the game tells you. There will be an on-screen direction saying "X" for "Grab." You can find a turd In the first chapter at the very beginning. When you are done pissing, turn right, and then go right into the shower room. There are stalls along the right wall. There will be a turd in at least one of the toilets in there. Be careful to grab the turd instead of flushing the toilet. For more information, here is a walkthrough for Duke Lives.