Just to expand on Drews good advice.
Instead of WD40 , I suggest a product that has a longer life on the metal. example, LPS2 or LONGLIFE, both available in aerosol can.
Spray liberally down the spark plug holes, around the valve gear, and in the intake ports if possible . Replace spark plugs.
Blank off the inlet and exhaust ports and wrap the engine .
I have successfully stored an engine like this for 10yrs. I pulled the wrapping off at 5yrs, rotated the engine by hand, redid the spray and re-wrapped it.
The big deal seems to be stopping condensation forming , so if your shed is warm' all's well, otherwise more oil is necessary.
