No, there is no simple/automatic way to install AIMP plug-ins, but you can do it manually pretty easy. You just need a compatible RAR archiver to extract the plug-ins and then a simple Copy-Paste operation.
Firstly, download WinRAR or 7ZIP to extract the archives. Secondly, access the AIMP plug-ins page to download them. Select a plug-in and download it, then extract its contents to the following folder: c:\Program Files (x86)\AIMP3\Plugins\. Make sure AIMP is closed, then start it and the plug-in will be available in the Plugins menu (Wrench icon > Plugins).
Plugins page: http://www.aimp.ru/index.php?do=catalog&id=2
