By default EndNote X8 installs only the commonly used filters, output styles and connection files. To install all available files, chose Custom instead of Typical during the installation process. Doing this should mean you don't need to add files at a later date.
1. Select the Custom option during installation.
2. From the drop-down menu of Additional Styles, choose Entire feature will be installed on local hard drive. This is the most important option, but we recommend you also repeat this step for Additional Filters and Additional Connections.
3. Click Next to proceed and complete the installation. You can leave the rest of the installation options as default.