First of alls - Gantry 5 website - http://gantry.org/ & Gantry 5 Documentation - http://docs.gantry.org/
Purposed to change the default Browser Scroll Bar on WebKit based Browsers !
This version has 14 Scroll Bar Styles, included most used & will be Upgraded from time in time !
Basicaly, the installation it´s veery Easy : )
Upload in your theme folder the /particles & /css folders !
Some like /public_html/wp-content/themes/th_heavenshop/custom/ - Here Upload both folders.
Some like /public_html/templates/th_heavenshop/custom - Here Upload both folders.
This it´s designed as particle 2 can customize each page, so you need to drag & drop this particle on the pages which you need to appear !
If you wish to be an atom , to use by default in your website with others Gantry atoms, then modify : scrollbar.yaml
name: Scroll Bar
description: Customize website scroll bar
icon: fa-header