I recommend you read the Installation section of the User Guide.
If you don't do so, at least follow these instructions:

Unzip the freqmanager.zip file to a convenient folder.  
* DO NOT unzip it to the SDR# folder for this will cause the plugin 
  installation to fail.

Please run program PluginsSetup.exe to install the plugins.  
* DO NOT install the documentation to the SDR# folder.

If the installer has no Next, Back, or Cancel buttons displayed, this is 
often because the screen's DPI (screen dots per inch) is set higher
than 100%.  Temporarily reduce the DPI to 100% and run 
the installer.

Thank you for using my plugins!

Jeff N8GJL