Hi here we are going to do a theme change for our magento default theme which would look like the following pic exclude the header section.
now login to your admin panel
And go to Magento connect manager
Magento again ask you to login . use your same username and password and login.
Click Magento connect to go that website
Choose Your theme and click install now agree the terms and condition and copy the key provided by magento connect.
And paste it in the test box as shown bleow
Click proceed to continue.
Then go to system>Design
choose your theme as shown above
then refresh your home page you can see the theme change as below .. if you are working on a server directly be patient for some time it may take some time to change
Thank you and hope this may help you .
T.mahes's Blog 