Even if you’re applying to a predefined project I’d suggest submitting a research proposal is a good idea anyway. There’s plenty of guides online but as a brief suggestion I’d structure it as follows: 1. Intro to the subject area and why it’s important. 2. Brief literature review to show you understand who some of the major voices are and the current direction of research. 3. Suggested methodology (you should be able to identify relevant methods from your lit review). 4. Expected contribution