If you are using a DIY sunroom kit, they are not as energy efficient as sunrooms built by professionals, so improve your efficiency by building on a slab foundation with at least one brick wall as a support.
Purchase a DIY sunroom kit and hire a contractor to build it, or build it yourself and hire contractors to finish the plumbing, HVAC and electrical if you are outfitting the room with these utilities.
Before you go ahead with the transformation, have a professional check the room to make sure it can handle the weight of a sunroom so there are no structural problems after the sunroom is built.
Before you can begin determining what type of sunroom windows you require either for a new sunroom addition or for replacement windows, you need to determine the type of sunroom you have.
Don't take on this job if you don't already have some type of construction experience; building a sunroom is a very difficult job requiring plenty of heavy machinery and powerful tools.