How I can creating D-Mods?
You can be looking at sticky threads at board top.
You should be able to go to the sprite screen by pressing E. For going to the next page, press ] or for Windinkedit, press Page Up. For going to the previous page, press [ or for Windinkedit, press Page Down.
He just told you about sprites, stuff like grass and cliffs are tiles. Press T (i think) to enter tile mode then use 1,2,3,4,5,6,7,8,9,0 and u to access the different tile pages. Also, do not use the numpad for the numbers.