I think it is important here to give specific advice. This is due to the generally poor advice I think I have had in terms of writing. Assumptions are made that good students are good writers already. This is not the case - the key difference between essay writing and the thesis is the process of writing.
When I was writing essays for my A-levels, I could draft, in one go, an essay that would get a B grade. They were short enough not to need drafting or editing. Thesis writing hit me for six - it was hard to write such long chapters and I had not been prepared for this as I had gone to a very ordinary school and community college. In the past, PhD students were elite brainiacs on the whole who needed very little supervision to get their PhD. This is why today; we have many issues with supervision because the PhD intake is far more diverse.
The key thing I have found (and not been taught at all) is that write a load of rubbish first. Yes! Look at what you chapter is about, read about your topic then write, just write. You then need to edit what you have written several times before it is ready. You might read and re-read articles, but you can't write a chapter in one go - getting words on paper is the most important thing to build confidence. Focus on writing training in this regard is still only just coming into universities which I think is shocking as I felt I was under supported.