after you export the textures, it's a matter of putting the roughness, metallic and ambient occlusion textures into DCS's required channels.
R = AO
G = Roughness
B = Metallic
Then you put it in the specular level channel.
You will also need to adjust the channels to look good in DCS because ED doesn't have any shader support for substance. What you see in substance wont necessarily be the same in DCS.
basecolor and normals should be obvious :
Now, because ED allows turning off PBR mode, you will need to name the new texture exactly the same as the original diffuse file, but with '_RoughMet' after it.
In the description you will add this....(for example)
{"PLANE_FUSELAGE", 0 ,"Plane_Fuse_Dif",true};
{"PLANE_FUSELAGE", 1 ,"Plane_Fuse_NMp",true};
{"PLANE_FUSELAGE", 2 ,"Plane_Fuse_Spec",true};
{"PLANE_FUSELAGE", ROUGHNESS_METALLIC ,"Plane_Fuse_Dif_RoughMet",true};