[Orgmode] How to use FILETAGS?

[Manish]

Hello All,

  I have set a "#+FILETAGS: :Personal:" in my org file (did a C-c C-c
to initilalize it.)  The tag did not appear in the agenda view like I
expected it to.  I was hoping to use agenda view filtering on tags to
see a subset of tasks with that tag (without having to set that for
all tasks.)  What else do I need to do for it to work?

-- Manish