GeoSWMM has been developed as an add-in for ArcGIS^® 10.x. Desktop system requirements for ArcGIS^® 10.x are available on the ArcGIS^® resources web-link at:
http://help.arcgis.com/en/systemrequirements/index.html#//015100000002000000

A user must have ArcGIS^® 10.x installed on the computer prior to the installation. GeoSWMM is available for download from the Streams Tech's product page on:
https://streamstech.com/Products/GeoSWMM

Detailed instructions on software download, installation, activation and upgrade are available for registered users on their My Products page.