I've done a presentation like this. I'm not sure which department you're in, so this advice might be way off. But for a Humanities proposal, I found that a "poster presentation" sort of outline can be handy.
If you can spend 30 seconds or so on acknowledgements, and another minute on the specifics of your project, that leaves you with the majority time to really hammer home the two most important things (in my opinion): what contribution you hope to give to the field, and why [insert uni name here] is the best launch pad to do that from.
The fact is that universities want to recruit research students who have the brightest possible futures. This means having a clear understanding of what has been done in your field (background), what you're hoping to do (method/framework), and most importantly, what this could mean in the larger picture (attention to the university, a breakthrough for you, a new angle on an old issue, etc.).
The second part to this is being able to show that you understand your place in the faculty. You should know the basics at this point, but if not, put together some background information on key members of faculty and their interests. If a method has been pioneered at that university and you want to use it, mention this. As much as you need to answer "Why me, as the student?" you should answer, "Why you, as the institution."
Best of luck getting through it!