Vanilla Forums is a very customizable, flexible platform because there are many ways to hook into it without ever modifying its code.
Before Vanilla 2.5 there were plugins, applications, and themes. Starting in Vanilla 2.5 all 3 of these have been combined into 1 format - Addons. An addon is capable of doing everything that each those 3 used to do.
Please read the documentation how develop addons.
Copy the folder contents into the plugins folder of Vanilla Forums.
The plugins folder holds all addons for Vanilla Forums.
Clear the entire contents of the cache folder.
The cache folder is located underneath the root Vanilla Forums folder.
There are no any button to clear server cache in Admin dashboard.
Clear browser cache.
Go to your Dashboard, then Settings, and select Addons at the bottom of the list on the left
hand side panel. Navigate to the addons list and click Enable next to the plugin.
Enabling the addon immediately makes it active and available.
After enabling some plugins will have a Settings 3-strip button that appear next to them in
the Addons list.