Maybe you should go to the library and do some background reading on presentation skills and techniques. If possible, attend a presentation skills course yourself.
I think it is quite unusual that your boss sends you as an inexperienced teacher to teach presentation skills.
Anyway, don't worry. Your students will probably know more about it than you. If you are lucking, they might just want you to check their pronunication and grammar.
By the way, there is an excellent textbook by a guy called Mark Powell on this subject. Sorry, but I just can't remember the title and the publisher off the top of my head.