Interface/WorldMap/(mapname)/..
Put your map files into this directory. Their names should be (mapname)1.blp - (mapname)12.blp. World map consists of 4x3=12 files (at least usually). Thats about BLPs, now about DBCs, you need to open WorldMapArea.dbc. Enter correct map ID, your chosen (mapname) and corner coordinates (those are server coordinates here). They are in following order:
field 5: bottom X
field 6: right Y
field 7: top X
field 8: left Y
At least as far as I know, maybe I have some mistake there. But it should be so and worked for my map. About that tut, sadly I don't know where it is.