You do not. All the resource manager allows you to do is HOST resources. The install routine is part of the core installing for add-ons.
@Chris Deeming and @Waindigo have add-ons that extend this function that you can install.
An add-on (like any of the styles) or FAQ, custom code, graphics, etc. You can see them at http://xenforo.com/community/resources/ here. All those (or most) are served by this site. Some link to other sites or pay-gates.
To install the add-on you normally have to upload the associated files to your site in the appropriate area then go into the ACP and on the Home Tab you see an option referring to add-ons. Select Install Add-On and then you point it at the XML file that you normally have extracted to your local computer (after uploading the files via FTP/SFTP).