I'm not familiar with a json file or Google blogs in general, but I'll try to offer some starting help.

First, as far as where to save it - you can probably save it anywhere you want to such as in 'My Documents' (or just 'Documents').  Just remember where you put it.

As to how to read it, the first thing I would do with a file with an unknown content is to try to open it with a simple ASCII file reader such as Notepad or even WordPad.  Open the application (Notepad or WordPad) and then try to open .json file.  Or try to open the .json file and it will probably not know how and ask you to choose to let it find an app on the internet or choose from installed programs.  Go with choose from installed programs and look for Notepad or WordPad.

If the content of the file looks "normal" and is not just a jumble of strange characters, letters and numbers, then that may be enough.  If it looks like a pretty well organized list of text entries and such, you might try saving a copy of it with the .csv file type indicator and then try opening it with Excel to see if that gives you a nice arrangement of data.

Your other option, barring more help here would be to try to get some help from Google support.