Your basic 5-paragraph essay is a good starting point if you're not sure what you're doing. Keep in mind, the most important thing, though, is starting a new paragraph when you switch to a new point of discussion!
What's the rhetorical situation of your paper?
What is your paper doing? A persuasive paper is going to sound different from an informative paper or an argumentative paper.
Who is the audience of your paper? Ask your professor who you're supposed be writing for. This will impact what you need to explain -- e.g. if you're analyzing a movie, should you assume your audience has seen the film, or do you need to summarize the plot and characters?
This also reflects the way your paper is written. A personal reflection paper about a short story made you feel is going to use lots of "I" statements and sound pretty casual. An informative research paper, on the other hand, should be more polished... you're not trying to use "big words" just for the sake of sounding fancy, but you do want to sound rather more impersonal than that reflection paper.
You can write a sentence in passive voice and be totally correct grammatically. However, it's a weak sentence. It's...well...passive. How do you know you have passive voice? Add "by zombies" to the end. Does your sentence make sense and sound good? You've got passive voice.
The person/entity/creature actually doing the action is buried way off in the sentence, if you bother to include it at all!
This is more likely to creep into your writing in a more subtle way.
Well, believed by whom?
"A much larger analogue of the asteroid belt, the Kuiper Belt is a cosmic junkyard, full of rubble thought to be left over from the formation of the solar system. But whereas the asteroid belt is made mostly of rock and metal, objects in the Kuiper Belt are composed largely of frozen water, ammonia and methane" ("Two Years On").
The Kuiper Belt consists of icy chunks of frozen water, ammonia, and methane believed to be "leftover from the formation of the solar system," much like the rocky field of the asteroid belt ("Two Years On").
Though both the asteroid belt and Kuiper belt are believed to be remnants of the solar system's formation, the Kuiper belt consists mostly of ice rather than rock, including frozen methane and ammonia as well as water ("Two Years On").
A bigger version of the asteroid belt, the Kuiper Belt is a cosmic junkyard, full of rubble believed to be left over from the formation of the solar system. But while the asteroid belt is made mostly of rock and metal, objects in the Kuiper Belt are composed largely of frozen water, ammonia and methane.
Work Cited (for above example)
“Two Years On, the Kuiper Belt is in Sight.” The Economist, 16 Sept. 2017, www.economist.com/science-and-technology/2017/09/16/two-years-on-the-kuiper-belt-is-in-sight.
There's no particular presentation format for MLA or APA or Chicago, but you still need to provide your citations. You'll have a Works Cited slide (or slides, if you have many sources) at the end of your presentation. You also need to include in-text citations on the relevant slides, just like providing in-text citations for papers.
When presenting, you can include citation information by mentioning, "According to the CDC's website, ..." or "A Duke University researcher, Dr. Juanita Doe, has suggested in a 2016 article that...."
A good rule of thumb is to have one slide per minute of presentation (i.e. for a 10 minute presentation, you should prepare 10 slides -- not counting the title slide or Works Cited).
A presentation requires every bit as much work as an equivalent research paper, but you won't show it in the same way. Presentations should be heavier on visuals and light on text: the information is being delivered orally rather than you writing it all out.