Usually, when you're talking about what people said with a word like "tell" or "talk about", you follow it with a noun:
He used to tell me about his farm.
If you want to explain an action, you use the "-ing" form of a verb:
He used to talk about waking up at the crack of dawn to work on the farm.
But what if you want to express a whole sentence that someone talked about? One way is with "how":
He told me about how he hated getting up so early every day.
He also talked about how his parents wouldn't let him go to school some days if there was too much work to be done around the farm.
Once, he told me about how his father didn't even know how to read.