Hi,
The demo for free version is not available. The Prayer PRO theme comes with ready to use demo content that allows you to set up your website as like the demo theme.
To customize this free theme, first create all pages for slider, services and welcome section with Featured Image
Then Go to the Appearance -> Customize -> Theme Options Panel -> Slider/services/welcome -> Select Page
Please check the documentation
http://www.gracethemesdemo.com/documentation/prayer/#homepage-lite
Regards
Grace Themes