How do I decompile a selected assembly?

Hi there,

When I have an assembly selected from the assembly explorer on the left, what do I do next to get it decompiled? I tried every menu and clicked on every clickble item but still couldn't figure it out. I know this sounds like a stupid question, but I am totally new to this tool and, as a matter of fact, I just downloaded it less than an hour ago...

To show you where I am at I have attached my current screen shot.

Please show me what I am missing here.

Thanks in advance!

Lifeng