It's simple.
Load your skybox(A skybox is just a cube with inverted normals and a texture) Depending on the scale of the skybox you may need to scale it(A tip is to have you skybox size at 100 then when you use the scale object command you can just type in the sizes you need)
sync on
sync rate 60
hide mouse
load object "Skybox.x",1 :`you must have a x file named skybox in the programs current directory
scale object 1,150,150,150
position camera 0,0,0
do
rotate camera camera angle x()+mousemovey(),camera angle y()+mousemovex(),0
sync
loop
You may also want to look into the "set object light" and "set object ambient" commands to get it to look right.
DBPro, limited by the programmer.