Hi Raj, welcome to the community!
When you setup a new instance of Joomla there is a couple of little tweaks you got to do before stating using. Some of them involve setting up the correct write permissions for some directories.
The issue you are having is related to one of those directory permissions. The cache directory is defined on the Global Configuration trough the administrator area. Please check the path for you cache directory, and set write permissions for all (777). It should fix your problem.
Let me know how does it goes.
PS: For future posts please related to General Joomla issues please post under "General Discussion"
Jose Soares