How to damp proof prefab garage to make office

[matty_hunt]

Hi. Im after some advice and options please. I have acquired a sectional Marley prefab garage, not yet erected, which I want to place on a hard standing next to my current garage. I want to use it as a studio for painting/storing canvases and upcycling furniture so needs to be damp proof to protect the canvases from mould. I also want to insulate it. Currently I have two plywood sheet doors but am looking to replace them with reclaimed patio doors and no roof. What would be the way to damp proof this garage so I can make it a workable space? I wasnt sure if a garage floor paint with a masonry paint on the sections would be sufficient to stop damp penetrating. Any ideas welcomed. Thanks