Changing the Default Template
You can download many free and premium (paid) templates from many places on the internet to change the look of your Joomla site.
Template Monster
Rocket Theme
Joomla-Templates
1. From your admin panel, go to Extensions -> Install/Uninstall.

2. Select the Choose File button in the Upload Package File box.

3. Browse your computer for the template file and then select Upload File & Install.
4. You should receive a confirmation that the install was successful after the upload is complete. To apply the new template to your site, go Extensions -> Template Manager.

5. Select the radio button next to the newly installed template and click the Default icon at the top.

Your template is now applied, you can click on the Preview link in your admin navigation bar at the top to see the changes.