You need to change the file type back to .zip, then extract the .zip file, to find the Presets.
The Preset pack has a .txt extension, since the forum only allows certain file types to be uploaded.
After you’ve downloaded it, change the file name, and remove the last four signs (.txt).
You can ignore the warning pop-up.
Then, follow the instructions on importing and exporting Presets to add the desired Presets to your drop-down menu.
From v1.1.22.0 onward, FxSound supports up to 20 additional Presets, and even supports up to 100 additional Presets, if you follow the instructions carefully.