It’s very important that you prepare for your presentation. Rehearsing has several benefits. First, during your rehearsal you can save timings that can be used to advance your slides automatically or record a narration. Even if you don’t use those timings to navigate your presentation, they help you anticipate whether your presentation will go under or over the allotted time. In addition, rehearsing helps you spot problems in running your presentation, such as animations that take a long time to play or type that is hard to read.
Attach a microphone to your computer.
Click the Slide Show tab.
Click Record ...