Constructing a pinhole camera is easy to do with normal household items. The last three items on the list can be purchased from any photographic supply store. You will need to collect the following items:
Paint the inside and the lid of the oatmeal canister flat black. This prevents light from getting in and being reflected which will do strange things to your image. Use the razor to cut a 1 inch square in the center of the canister. Use the heavy duty shears to cut a 2 inch square from the soda can. Flatten the aluminum square and use a regular sewing needle to drill a hole in the center. Sand the hole until it feels smooth and appears round. Use the black electrical tape to adhere the pinhole (aluminum square) to the outside of the canister. Use another piece of electrical tape as a make shift shutter. You now have a working pinhole camera.
First you will need to find a light-proof room, like a closet or bathroom without windows or completely covered. The safelight will not expose your photo paper but offers enough light to see what you are doing. You will load a sheet of photo paper in the back of the canister- the curve will hold it in place. It is imperative that you place the emulsion side out- facing the pinhole. The emulsion side is shinier than the back in most cases. Once you seal the lid, you can turn on the light and go outside to take your picture. Exposure times will be trial and error at first, but a good starting point is 30 seconds for a sunny day. Partly cloudy may require twice that- 60 seconds. In the shade could be 2-4 minutes. Inside a well lit room can take several hours.
In a dark, light proof room, set up your trays with the chemicals mixed as per the manufacturer's directions. Developer in tray 1, Stop Bath in tray 2, Fixer in Tray 3. You will need to have access to a sink with running water to wash your prints. The developer will react to the exposed emulsion and the light areas appear black. Develop your print for up to 2 minutes. The stop bath halts the developing process- just 30 seconds. The print then needs to go into the fixing bath for 5 minutes. The fixer hardens the emulsion. At this point you can turn on the light. Wash you print in a sink with clean running water for 10 minutes. Then you can either blot or hang your print to dry.
You will notice that your image is inverted. You will need to either contact print your image on another sheet of photo paper- another trial and error process... Or you can do what I do and use a scanner to scan the negative and use a photo editing program to invert it.