I have struggled with this myself, but basically the structure of your essay will largely depend on what the question asks of you and your preferred writing style, there are so many ways to structure it, and all of them are right, as long as you are able to answer the question.
Personally, I prefer to do one paragraph per principle belief and here is a basic structure
Paragraph 1: Salvation with links to the ultimate goal of Christian living and how many denominations deem it a necessary practice to achieve salvation (e.g. Catholic and Orthodox)
Paragraph 2: Death and Resurrection of Jesus, talk about the symbolism of water and how the act mimic the Jesus dying on the cross and rising from the dead
Paragraph 3: The nature of God and the Trinity, talk about the use of the Trinitarian formula (sign of the cross) to initiate and welcome Christians as disciples of God into the Church and follow the example of Jesus
Obviously, you need to make consistent links to the question and make sure you are answering what the question is asking + ensure you use appropriate biblical evidence throughout
I hope this helps!