Use this shader:
http://www.opserver.de/wiki/index.php/Normalmapping_Shader_With_full_specmap_supportCopy it into SED, and save it as a .fx file.
Now you need a normal map, and a specular map.
Open MED...
Load your first skin, the diffuse (color) map. Make sure you've ticked the "Material" box at the top. Then select "Effect Setup" box, and load the .fx file you saved the shader as.
Click "New Skin", and load the normal map. DON'T apply it to the model. Click "New Skin" again, and then load the specular map. DON'T apply it to the model either.
Now apply the diffuse (color) skin to the model. Then go to File>Save, and save your model. Now you can go to File>Engine Preview to view the results, or just use it in your game.