[Blender] How to make a rigging "With Automatic Weights"?

[kit1858644]

Hello, I want to making WW animation, I'm new in Blender and found Blender official tutorial in YouTube, but I have some problem:

 

I download WW rig in WW Creating Basic Animations In Blender, but I found the rig without "With Automatic Weights" some like this:

 

In my own try to build my own bone and add "With Automatic Weights", in WW rig, I can't select rig mesh to add "With Automatic Weights".

 

Is anybody can help me with this.

 

Thanks

 

 

I want to add "With Automatic Weights" because the rig will like :