You need at least one 3D modeling program and a graphic editor. There are several ones available. You can get them for free or for a fee.
Choose whatever you like best. Well-known 3D programs are Rhino, SketchUp, Blender. Graphic editors are used to create textures and to eventually manipulate the unfold on the canvas. You may use Photoshop, Gimp, CorelDRAW. The model is virtually built in the 3D program, textured and then unfolded.
If you delve into the matter you may get to Pepakura sooner or later. This is a special unfolding program which has two windows: One showing the completed model and one showing the unfolded parts. You may manipulate the unfold by moving parts around, sub-dividing them into smaller parts or joining them to bigger parts. You may also change the texture map if necessary. It is no modeling program but serves only to manipulate the unfold and give you a view of the finished model as a guide.
If you want to start making an own model I suggest to try free software first to get a feel for it.