Install NSIS as thats the engine that creates the installer using a script, you can wiite or edit the script yourself but theres a whole raft of really helpful editors about including the one i use, install one of the editors after installing NSIS and that should help you with the install script or in some cases generate the file based on the data you inputted.
The file folks will require is found in the "Release" or "Debug" folder as the output from your IDE or Visual studio. project. you basically have to set the installer to place the bendmx.dll file into the winmx folder its pretty easy stuff.
Create yourself a test folder and then change the install path if things work ok in the test.
PS: As this is open src you'll need to either share the parts you have updated with a link to the original src location or share the whole src in a compressed archive, I usually go for the sharing of the new part and a link to the old files to save space , a third option is to share the whole src from a web location if that helps.