The unzipped file is SendPostData.dll which should be copied in the folder
C:\Program Files (x86)\Vstep\ShipSimExtremes\channels
in order to replace the obsolete existing file, which means that you should allow windows to replace the old file.
If you prefer, you can also firstly delete C:\Program Files (x86)\Vstep\ShipSimExtremes\channels\SendPostData.dll and then copy the unzipped file in the said folder.
Good luck with that,
Luc