I have installed Variety wallpaper on ubuntu but how can i make it work

Which version of Variety did you install on which version of Ubuntu, using which desktop environment? What exactly does not work - do you see an indicator icon, can you interact with it, can you open the preferences window?

I have ununtu 12.04.
There is no indiacator icon after installation.
While in software center it is showing that variety is installed.

Should i reinstall it ?
Thanks in advance.

Indicator icon appears after you run it, not after you install it. Did you try to run it?
When you open the dash (press the windows key) and type "variety" do you see its icon - a green and black icon?

If you see it and run it, but it doesn't appear as an indicator, then there is some problem. Please run "killall -9 variety", then delete the folder ~/.config/variety and try again to run it. If it still does not run, open a terminal and run manually "/opt/extras.ubuntu.com/variety/bin/variety -v" and check the log if it reports some errors.

If you don't see it installed at all, there is some problem with the installation - uninstall it, and follow the steps in http://peterlevi.com/variety/how-to-install/

From the comments on the site:

I tried your solution and here is what the terminal messages stated:

.....~$ /opt/extras.ubuntu.com/variety/bin/variety -v

INFO:variety: process_command() 'Received command: ['-v']'
INFO:variety: load_banned() 'Missing or invalid banned URLs list, no URLs will be banned'
WARNING:variety: load_history() 'Could not load history file, continuing without it, no worries'
Traceback (most recent call last):
  File "/opt/extras.ubuntu.com/variety/bin/variety", line 46, in
    variety.main()
  File "/opt/extras.ubuntu.com/variety/variety/__init__.py", line 87, in main
    window.start(arguments)
  File "/opt/extras.ubuntu.com/variety/variety/VarietyWindow.py", line 117, in start
    self.thumbs_manager.mark_active(file=self.used[self.position], position=self.position)
IndexError: list index out of range

This is a bug in the code. I managed to reproduce it by setting a solid color instead of an image for a wallpaper, then running Variety. Please set a valid existing wallpaper image from Ubuntu's Appearance settings and try again.