Hola

There is no article or lesson on how/ when to use commas in Spanish. Rules for punctuation are very similar in Spanish and English (with differences though) and pauses in the discourse doesn't always mean punctuation. Punctuation is actually more related to functionality of the different elements in the sentence. 

We plan to add more articles explaining punctuation though, but it is quite complex. Have a look at all the "rules" for the "comma" here for example. 

Just so you know, you shouldn't worry too much about punctuation when you practise our dictations as we don't penalize it. The aim of these listening exercises is not focused on writing the right punctuation. 

Saludos cordiales