Hi,
To install the theme on your website
– Go to the menu Appearance > Themes and click on Add New button.
– Click on Upload Theme button.
– Click on Browse button and navigate to the unzipped theme package on your computer.
– Look for a file called polity-pro.zip Click on it to select, then click OK.
– Click on Install Now button and wait until the installation is complete.
– Click on Activate link to activate the theme on your WordPress site.
– Go to Appearance >> Theme Options >> Restore Default.
Please check the documentation
http://www.gracethemesdemo.com/documentation/polity/
Regards
Grace Themes