According to the book there is a part called "Creating Panel page".
This part had some steps to create a panel page. The 6th step said that
"Define a context: add the argument3 “node ID” (fig 4.6), select the
content type Profile (for content type and own display).".

my problem is where i can define this context?
when i going to define a argument that says 'No context assigned'.
And when i click the change button, its nothing happens anything but a loading screen pop ups and load for a long time.

please help me..
i am new to using panel module