I don't know what the professional registration requirements are, but you probably want to find someone with a registration, and who has public liability insurance.
After that you'll want someone offering an evidence based therapy. CBT has good evidence, but there are others.
Then it's just who you get on with. You'll spend about an hour a week, for about 10 weeks, with this person, so you want to be able to talk to them and feel that they understand you.
If you can cope with self guided from a book you can get Mind Over Mood. This is sometimes used in some English NHS settings.
If you can cope with self guided from a computer you can try Mood Gym, a well respected Australian website.