The introduction to this article is a good general account of who the sophists were. There’s also a section on Protagoras’s Relativism, and in the part on nature and convention, there’s a paragraph on Callicles’s egoism that should help draw the link with Nietzsche. The entire article is a good read in any case so I strongly encourage second year Advanced students taking the exam this May to find time to read it.
Don’t feel you have to remember everything in the article, but first of all, just try to get a general feel for who these “sophists” were. Take notes on the relevant sections but again, don’t think of these as a list of “points” to memorize; rather, they are a sketch of your understanding. The important thing is to understand something. Then, just before the exam you can re-read your notes to refresh your understanding.
This is the sort of research you need to start doing alone, by the way. The only way to gain philosophical depth in your writing is to broaden your understanding. And to do that you need to read, read and read more. Then, it will be so much easier to write about your topic that the problem will be knowing when to stop 😉