I believe what you are doing in this file is linking the .sco file to the correct terrain code. Basically this entire file is filled with the same type of lines, split over different categories. Find the right category and create a new entry. Below are the latest 4 entries from the DTV category.
("dtv_motte_and_bailey",sf_generate, "none", "none", (0,0),(100,100),-100, "0x000000052000460780059d67000005f8000062dc00005a3d",[],[],"outer_terrain_plain"),
("dtv_lichens_island", sf_generate, "none", "none", (0,0),(100,100),-100, "0x00000005500009e38004d13600001d5e80002318000060a1",[],[],"sea_outer_terrain_2"),
("dtv_desert_ruins",sf_generate, "none", "none", (0,0),(100,100),-100, "0x0000000151065463000689a6000000fe00000c690000276a",[],[],"outer_terrain_desert_b"),
("dtv_celtic_ruins",sf_generate, "none", "none", (0,0),(100,100),-100, "0x00000001b004c563c006559500001c9e000010b4000035f9",[],[],"outer_terrain_beach"),
What you want to do is create the exact same type of entry and place it at the bottom, but with the name of your .sco, your terrain code and outer terrain type. Which would look like this (bold parts are changed, the rest is just copypasta)
("
dtv_terrible_map",sf_generate, "none", "none", (0,0),(100,100),-100, "
0x00000002200005000005f57b00005885000046bd00006d9c",[],[],"
outer_terrain_plain"),