Learn French: J'ai écouté le bulletin ce matin. - I listened to the bulletin this morning.

The passé composé is used because listening to the bulletin was a specific, completed action that happened in a finished timeframe (ce matin). You would use the imparfait if you were setting a background scene, such as "I was listening to the bulletin when the phone rang."

Could I use j'ai entendu instead of j'ai écouté?

It would change the meaning slightly. Écouter means to actively listen to something, while entendre means to simply hear it. By using écouté, the speaker implies they intentionally tuned in and paid attention to the broadcast, rather than just hearing it playing in the background.

What does le bulletin usually refer to in everyday French?

In the context of morning broadcasts, le bulletin usually refers to a short news update (un bulletin d'information) or a weather report (le bulletin météo). It can also mean a school report card, though that doesn't fit this context!

If I wanted to report what the bulletin said about the future, how does this past tense affect the rest of the sentence?