The Extension Manager dialog box is a central location for managing ReSharper extensions. Using this dialog box, you can find new extensions, install and uninstall extensions and get updates.
Click Settings to configure the list of NuGet package sources using the Environment | Extension Manager page of ReSharper options.
Starting from ReSharper 8.0, extensions are installed and managed with NuGet. However, legacy plug-ins are also supported. The Environment | Plugins page of ReSharper options displays both legacy plug-ins and NuGet-based extensions.