To make the job easier use a circular saw to cut the plywood sheet first into 2 2 8 strips which will be much easier to handle.
Reasons to put plywood in attic.
The decision regarding the thickness of plywood to use for the subfloor in the attic has a lot to do with how you intend to use the attic and it also depends on the spacing of the ceiling joists.
Maneuvering heavy 4 x 8 sheets of plywood or osb oriented strand board up to an unfinished attic is sometimes like trying to fit a square peg into a round hole.
But if the floor is covered in plywood you can t stuff enough insulation beneath it to do the job sufficiently not even in warm climates.
The plywood should be perpendicular to the joists so that a signal sheet spans multiple.
Stop using your attic for storage.
If your attic joists won t bear the weight necessary to finish out a living space but the engineer cleared them to support floor decking for light storage you can install inch plywood or.
Carry a piece of plywood to one of the far corners of the attic and lay it on top of the installed boards.
So you can put 8 inches of insulation down then put the plywood over that.
Plan to pull up the flooring and layer new insulation on top of the old.