Help me with importing Picture as a change to minimap

Help me with importing Picture as a change to minimap

I want to change the minimap picture with custom TGA. I tried to do this many times,even looking for Blizzard maps, but i failed
how to do it?
P.s. If this topic was discussed earlier, please, don't beat me

import your file

change the name To:
war3mapMap ( if you want to change the ingame minimap )
war3mapPreview ( if you want to change the preview )