This is the guide you want. It’s in the first post and it doesn’t have the steps you’re describing. Take another look.
Depending on whether you do a manual download or multi-part download the steps are a little different.
If you want to do a manual download, the first step is here.
For that method, you still may have to download 2 parts. Might that be your problem, that you don’t have all the parts?
That said, I would not personally recommend that method, though.
I would recommend a multi-part download since it divides a really huge file into smaller pieces. The first step to that is here
But either way, the steps are in the guide, and you are having trouble because you aren’t following it. There’s nothing in there about a PPT file.