Long and short is that its uses are similar, if not identical, to English, though the rules surrounding its usage are less grammatically strict. This looked fun to translate, though, and doable, so I made an attempt below. Had to use dictionaries to pick up a few unknown kanji. Maybe someone else can smooth over the patches that were rougher for me!
"Though commas may be written various places semantically, there aren’t exact rules for their usage. When it comes to conversations, we usually use commas to indicate short pauses.
Commas tend to be placed after roughly every ten to twenty characters, though there are many reasons why they may be used after fewer.
-Immediately following a subject (Ex.: 私は、あしたがっこうに行きます。) (This is such a Japanese-specific case, I don’t see a way to translate it while preserving the comma usage; here it is minus some kanji.)
-In situations where you’re listing several words (Ex. I went to Tokyo, Osaka, and Fukuoka.)
-After a conjunction or interjection (Ex. Therefore, after all, oh, etc.)
-After a conjunctive particle/phrase (Ex. He said that, and followed me.) (Not sure on this one!)
-After phrases that signify times or conditions (Ex. After an hour, the thing I’d been worried about happened.)
-To break up meanings/ideas (Ex. She was smart and cheerful, a person with a beautiful smile.) (Also not sure the way I’ve phrased this really helps present the rule. This is another case where I don’t think there’s a way to carry the comma usage over into English that wouldn’t be at least somewhat awkward.)"
Hope this at least provides a decent start!