To install a new plugin on SilverStripe, follow these steps:
Browse to the SilverStripe add-ons website and download the plugin you wish to install.
Extract the archive contents to a new directory.
Change the directory name to the one specified in the installation instructions.
Place this directory in the site root directory at /opt/bitnami/apps/silverstripe/htdocs.
Browse to http://SERVER-IP/silverstripe/dev/build to rebuild the database.
Browse back to the application and the plugin should now be installed.