Primary research isn't an essential. I had no primary research in my Extended Project whatsoever, and relied solely on secondary resources but still got an A*.
I'd start off your secondary research by breaking down your question into a series of more manageable key questions, then research each of the smaller questions. Find some reliable websites online and note them down, before you start going more in depth and looking into relevant books and articles, journals etc. But yeah, don't worry about primary research because you don't need it.