She or he can help you locate other sources, such as the course or module leader. The course and module documents will talk about the aims and objectives of your module, and of the course as a whole. Oh, the other reason you're doing it may well be money. Decide on the structure and the main points. If you and the students know the structure of the presentation right from the start, any stumbles you make will be much less serious.
Students can cope with being lost for a few minutes.
But if they fear they'll be lost for an hour, they may, understandably, get restive. This will give you great confidence that you won't dry up. However, it will take you hours to do. Work from cards or OHT slide thumbnails. If you're using a lot of OHT slides, the thumbnails of these slides, printed at six to the page, serve the same function.