Like, I set 1 to 23 in this page,
But when I select Test font or export to a ttf font directly, it shows up like this.
What I should do to apply those edits to the font?
You would need to select "Test Font 2333333337282 in the application that you are testing the font in and enable the subscript OpenType feature, while leaving the Font Test window open.
Where to enable it? Can I have more details?
Which word-processor or publishing application do you use that supports OpenType features? If you have nothing else, LibreOffice can be used, but enabling OpenType features is far from intuitive.
OK I downloaded it and then…?
The explanation on how to enable OpenType features is on the web page at the link.