ZBrushCentral

NEED help With textures

Hello everybody i need help with something i created a low poly version of character for a game
now i have 3 maps Difuse specular and bumb map how can i put these 3 files into one psd
i just simple make 3 layers? in one psd? and every layer is each file?, is that simple or do i have to do something more specific? I would be thankfull if u will answer to my question,