how to change normal maps from a texture

[EasilyUnstpp_]

i've been trying to change the textures from this sign in diner but it appears to only be changing the texture but not the normals. what do i to change the normal map too? do i convert the .tga files to .iwi the same way as i do it with .dds files?

[LKurama]

EasilyUnstpp_ I always export them as DDS files. Just leave a flat color on it and the job is done