Explain + Opinion + Accuracy + Purpose. Explain what the source is actually saying, quote a specific part to show your understanding, and use inferring vocabular "Source A implies..."
Next, express your opinion whether both sources are useful, compare which is more useful "to a historian". Accuracy, state whether certain parts of the source are accurate, or misleading by using your own knowledge. Purpose, talk about what it is (poster, diary, record etc.) and whether this is positive or negative to a historian. Talk about who made the source and at what time the source was created and whether this is positive or negative to a historian.