Step 1: Obtain a virus. The best way to do this is to hang around some sick people
Injecting yourself with dirty needles or rusty nails also sometimes helps. This is a good way to get the deadly tetanus virus-carrying chemical mentioned in that news article. The best place to find sick people is in a "hospital", which is a large building, full of the high technology where the baby-eating devil-worshipers house their sick and injured.
Step 2: Put the viruses into a bomb. The best explosive to use is nitroglycerin, because it won't hurt the viruses. Nitroglycerin may be easily purchased at any hardware store. After you mix them together, it's important to shake well to be sure they're well-mixed.
Step 3:If you're not 100% sure what disease it is, the note should be modified to say, "We have this disease". There is nothing more embarrassing than to tell infidels they will die of smallpox only to find out that you started a tetanus epidemic instead. This makes us all look stupid and it's something we really need to avoid at this point.