1-You need a conclusion that can summarize the key points you are making with the essay.
2- You need to make sure that you are answering the essay question. Just talking about one of the wars, and then about the other is not really comparing the two. Think about characteristic features which you can base your comparison on journalists, censorship, access, military-media relationship, etc.
3-Engagement with theory. You need Hallins spheres of influence when talking about Vietnam.
4- It will help your argument about Falklands if you mention that the media acted as a propaganda tool for the government, but make sure you explain why.
5-You dont need to compare and contrast the theories just use the ones that are relevant.