How to use sprite packer Unity 4.5

Questions & Answers
1

I cannot use sprite packer feature in my project at all. I enabled it in Edit → Project Settings → Editor. I can open the sprite packer window and see its button now. But when i click to pack button, nothing happened.
Then i reread the document again : Unity - Manual: Sprite Packer
I see this line but i have no idea what is it!

"Users are required to specify a **Packing Tag** in the **Texture Importer** to enable packing for Sprites of that Texture."

I used unity for a while but i haven’t known what are PACKING TAG and TEXTURE IMPORTER, and where are they …
Please tell me how to work with this feature, I am really appreciate!

2

Select one of the images you want to pack from your Project view. In the inspector window (aka texture importer settings, in this case), set the Texture Type to “Sprite” and you’ll see a Packing Tag field where you can enter a field. The name is up to you, but all sprites that use the same Packing Tag will be packed into the same atlas automagically.