Hiya.
Well, uh, you model it.
Again, there are probably a million ways to do it, but one way is to select the part of the model that would be the clothes (ex: the 'shirt'). Then duplicate/extrude/add thickness (depends on the modeling package you are using)...voila! A shirt. Then, go in a tweek it a bit here and there to add some randomness, apply UV, texture, and you're done.
I'm not very familiar with either MED or Blender (I use Hexagon2 and Softimage XSI), but blender probably has a way to select polygons and then extrude them to get your clothes. Here is an example of "polygon extruding clothes" (it uses Hexagon2, but the purpose is there):
http://forums.polyloop.net/showthread.php?s=a2015b0981338335d0bc993a8c605134&t=5842(you want to go down to Part 9, where it shows how he does the shorts for the character).