Are you still interested in using playSMS in Windows ?
Well, someone has wrote the manual for you in playSMS Forum. The manual is about installing playSMS in Microsoft Windows with Gammu for Windows as the gateway.
Check it out: https://forum.playsms.org/t/installing-playsms-on-windows/66
Please note that the playSMS in used was pretty old, version 0.9.9.2 or 0.9.8, and unfortunately the manual won’t work for playSMS 1.0.