Bake lightmap to export it to Unity3d!!

Hello
Let us make it simple so i could understand well :slight_smile:
Let’s say that i made a room, unwraped and textured ( Just a cube ) and i put a light inside that room.
How can i bake a light map so i be able to export it to Unity 3D game engine?
I tried to search Google but all i got an out dated tutorial that i can’t follow.

Can you just give me the steps to create a lightmap?