If you're pissing you just stand in front of it, as you might intuit. To shit you have to put your back to the wall, pull your pants all the way down to your ankles, and squat over the hole. It's a very fucked up, vulnerable feeling. If you have the squirts, it's really not the ideal design.
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"All my years in p*rn didn't quite prepare me for childbirth. I mistakenly thought all the stretching I did would make this easier."