Help how do I?

I'm assuming the engine is free?. Engines that have been dormant like your example should be dismantled in my opinion. Not necessary to initially run, Castor oil is probably one of the best preservatives out there in terms of longevity. The problem is it works too well. Areas of concern would be in the crank. The oil gums to the point of varnish. It will release enough to allow the crank to spin, but once the engine starts making heat and rpm's this stuff will almost grab a hold of the crank not allowing for full rpm's. I personally would dismantle the engine and give those areas a good thorough cleaning. This may even require soaking the crank in a solvent to help assist with the removal and even then it may require a polishing in a drill press.

The plug would also be a concern of mine. I certainly would allow it to set in solvent to break down all the goo that formed in the element cavity prior to lighting it off. A new plug is generally always best. The TD screw in venturi would also be a area that I would explore in terms of making sure all the holes in the sprinkler are clear of congealed castor. The other area of concern would be the tank gasket. Those tanks especially at that age are prone to leaks and cracks.

Next step would be having a good fresh battery and giving the engine one to two drops of fuel in the exhaust port and see if it lights off. It should rapidly respond to that. I would then place your finger over the venturi and rotate the prop looking for fuel coming up the fuel line. Don't overchoke the engine, just watch to see the fuel enters the spraybar. Prime again and give it a flip. Getting the needle setting initially is probably the trickiest part of starting. Ken