I've been told there's another Green Gym in Formby, this is sited in the recreational space at Deansgate Lane.
Following some research I came across this demonstration video explaining how to use this item. I hope it helps. I'm was going to publish a series of these but if you play the first episode you're offered some more short demonstrations. They're well worth viewing.
If you see anymore Green Gym installations please let me know. So far I'm aware of three others in Duke Street Park, Lifeboat Road parking area and at the Swimming Pool.