The Method

As seen on The Nuclear Boyscout

Gather materials, by tracking down radioactive sources as listed in the Boy Scout Atomic Energy Merit Badge Book such smoke detectors, lithium batteries, thorium nitrate, and thorium lanterns.
Extract radioactive thorium by blow torching lantern covers, adding lithium, and wrapping in tin foil. Heat this up in a cooking oil filled tin can.
Extract radioactive americium from smoke detectors by breaking them into small pieces, and looking for the radioactive bits with a Geiger counter.
Build a neutron gun to make elements radioactive. Take a lead block, put Americium from smoke detectors inside of it, and wrap the whole thing in tin foil. The Americium releases alpha particles, which makes the tin foil produce neutrons. Neutrons react with other elements to produce radioactive variants of the elements.
When enough material has been gathered, create a reactor. I won't tell you the steps for this one, it is easy enough to look up and I would rather not be an accomplice to informed stupidity. The purpose of this website is to inform the reader about what happens when a physics prodigy chooses the wrong route to fame.