Easiest and fastest way to install plugin is to do this from WordPress site plugin management interface. Alternatively one can follow the steps:

  1. Ensure that Relevanssi plugin is installed
  2. Upload the plugin files to the /wp-content/plugins/relevanssi-rest-api directory, or install the plugin through the WordPress plugins screen directly.
  3. Activate the plugin through the ‘Plugins’ screen in WordPress
  4. Plugin does not require any further configuration