I'd suggest getting some construction books on building, particularly greenhouses. Planning the foundation frame, and getting the sidewalls and roofing beams up will be important next. You may want help from a contractor due to the size.

What is it made of? A poly hoop type house? Aluminum and glass structure? not much info to go on here.

Thanks for your notes Kitty and Dave

Problem it is, to give you much information as I don't know much about it

Just looked at all the pieces stacked up on the patio in back of the house.

I was reading some that important to begin with is a good base to sit it all on

Maybe dig down ten inches I was thinking and put in a gravel base

Up here in southern Ontario, we get lots of cold and frost of course in the ground.
I agree he needs someone knowledgeable to come in and look over the materials.

It isn't glass though, Graham said, but plastic of some sort, but looks like glass.

There are sheets of styrofoam that I don't know where they go.

I wish I would have seen it before it was taken down. They did not take pictures of it before dismantling .
He will not be leaving the project undone as he is a fussy guy and keeps his yard and property beautiful
I fear though if it isn't done right, there will be lots of problems later

He has fellows to help him do the work, friends etc. But ...
Maybe your are right Kitty I will look for a book on the subject.