Downloading mails/news for offline usage

[nipra]

Hi,
  I recently set up gnus following steps at 
http://bc.tech.coop/blog/070813.html.
My ~/.gnus.el is as follows:

(require 'pop3)

(setq gnus-select-method '(nntp "news.gmane.org"))

(add-to-list 'gnus-secondary-select-methods '(nnml ""))

(setq gnus-permanently-visible-groups "mail")

(setq gnus-posting-styles
      '((".*" (name "Nikhil Prabhakar"))))

(setq mail-sources
      '((file :path "/var/mail/nipra")
        (pop :server "pop.gmail.com"
             :port 995
             :user "prabhakar.nikhil@gmail.com"
             :connection ssl
             :leave t)))

;; Configure outbound mail (SMTP)
(setq smtpmail-starttls-credentials '(("smtp.gmail.com" 587 nil nil))
      smtpmail-smtp-server "smtp.gmail.com"
      smtpmail-default-smtp-server "smtp.gmail.com"
      send-mail-function 'smtpmail-send-it
      message-send-mail-function 'smtpmail-send-it
      smtpmail-smtp-service 587
      smtpmail-auth-credentials '(("smtp.gmail.com"
                                   587
                                   "prabhakar.nikhil@gmail.com"
                                   nil)))

Now I want to configure gnus to download all mails from gmail and news
from selected newsgroups for offline use later one. What are the steps
involved?
Regards,
nipra