Check out my article Angela Booth's Writing Blog: Freelance Editing: Find Unadvertised Jobs, in which I gave you a process to follow:
"1. What Specialties Do You Have? Firstly consider your specialties. Publishing houses need specialists when they hire editors. If you've been writing articles for parenting magazines for example, you can consider yourself a specialist in parenting topics. Therefore, approach publishing houses which publish parenting books. Parenting is an extremely wide field, with many opportunities."I've recommended Twitter to several editors, who've managed to get jobs very quickly.