Not really sure where to start, need help..

Firstly remove spark plugs, spray a liberal amount of WD40 (US equivalent?) down each cylinder....let it soak for couple hours. Repeat spraying 2 or 3 times more, THEN ONLY try to rotate by HAND. Attempting to crank a locked engine may cause damage to starter motor, or internals of engine. Once you have it turning by hand, do the oil/plugs change.

There is more to firing up a no runner than simply adding fuel.

Keep us updated.

Ters.