ALWAYS make a backup of all of your theme assets, including CSS files, master pages, page layouts,...Reparing the theme will remove all custom changes you have applied previously.
Before reparing your theme, clean your browser cache.
1# Uninstall the theme
To repair your theme you need to first completely remove the theme from your website.
You can find the instructions for uninstalling the theme here.
2# Install the theme again
After completely removing the theme you need to install the theme again.
You can find the instructions for installing a theme here.