Congrats on passing the instructor course! I will lend a couple tips that helped me. I didn't gain these from a book or a course (although Toastmasters gives great tips on public speaking) but from experience in front of people.
1. Remember, in front of the crowd, you are the expert. They came to learn what you know, not to critique how you give the information.
2. Unless the people you are teaching are different from most groups I have taught, the worst thing they would do is walk out. They're not going to throw things at you or heckle you (
you're not planning on political speeches, are you?).
3. Sometimes starting off with a joke or something lighthearted will relax both you and the audience. I remember my first class learning ACLS and the instructor had us all chanting "Shock, shock, shock. Everybody, shock. Little, shock. Big, shock. Everybody, shock." This not only broke the ice but to this day reminded me of the algorhythm she wanted us to remember.
4. Then, of course, practice, practice, practice. No little tricks fully help unless you are putting them to work. Practice in front of mirrors, family, and co-workers. Put together small group teaching if you can, and sit down to teach them. This is relaxed and gives you more practice. Also if the setting allows for it, use a stool when in front of a crowd. That definitely relaxes me because it isn't so formal.
Good luck with your continued teaching!