You switch back to your DBC and go to that row. In my example with 28728 its:
28728,"","","","","INV_Pants_13",0,0,1,0,0,7,0,0,"","","","","","Robe_Horde_B_05 Purple_Pant_LU","Robe_Horde_B_05Purple_Pant_LL","",0,
You see: ID, model1, 2, 3, 4, Iconname, geoset1, 2, 3, 4, unk, groupsound, helmet vis data 1, 2, texture 1, 2, 3, 4 ... etc, itemvisuals. What is interesting to us is the geoset part. If you search for a leggings you get an entry like:
25833,"","","","","INV_Pants_04",0,0,0,0,0,11,0,0,"","","","","","Plate_A_01Silv er_Pant_LU","Plate_A_01Silver_Pant_LL","",0,
You see at the geosets: The leggings got 0,0,0,0 while a kilt has 0,0,1,0. Well that's all. Just change that field to 1. Its the 3rd after the Iconname. But I think you should find it if you search for an kilt and trousers to compare the entries.
I hope that's it.