I once again draw your attention to this thread. It shows the step you need to download and install GoG Falcon 4 and then how to install BMS. It was done on a Win 7 machine - so yes the GoG download goes into the Download Folder unless you save it someplace else using Save As.
Right click the Falcon Setup.exe and select to run as administrator - this should help with installing Falcon 4. Once you have it installed BMS is a breeze as it will find where Falcon 4 is automagically when determining if you have it before letting you install BMS. If you don’t have Falcon 4 (or haven’t installed it properly) the message displayed on your screen when you try to install BMS will leave you in no doubt and will even point you to where to buy Falcon 4 (a bit academic in this case).
Don’t give up at this stage. There are plenty of folks who are willing to help or even talk you through installing BMS. Take advantage to them if you are having issues …