Hello and apologies for the late reply. It has been a busy few days.
What you're getting is a .7z file, which is a more advanced compressing technology, but lacks native support from Windows to open it.
We recommend googling and downloading either one of the following utilities to open the package you get:
1) Winrar
2) WinZip
3) 7-zip
Of all these, we recommend 7-zip as our tool of choice. It's completely free and can not only open .7z files, but shares compatibility with .rar and .zip as well which is handy to have as it will help you unzip all types of files in the future as well.
Hope this helps!