Go outside, because you need a lot of sunlight for this to work; light is your worst enemy with the pinhole camera, unless you're outside.
You can measure your exposure by using this handy guide. Our photo (above here) was taken in a moderately-lit alley with exposure time of 1/4 a second—and the shutter was taped the moment it went back down.
You're looking at a photo of me standing in the middle of an alley in the daytime. You can make out the curbs of the sidewalk on each side and a white truck in the background. See that fetus-looking guy at the back, about an inch big? That's me! Obviously, the results could have been better, but you're looking at photo taken from a camera made out of a booze box.