Graswaldpro1.3.11dev_downloadpirate.com.zip -

: Click the Install... button at the top right of the window.

: Version 1.3.11 is older. Ensure your version of Blender is compatible (typically Blender 2.8x or 2.9x for that specific release). GraswaldPro1.3.11Dev_DownloadPirate.com.zip

: Find your GraswaldPro1.3.11...zip file and click Install Add-on . : Click the Install