This is a great short tutorial that explains the fundamentals of using Garageband, which is the free audio and music production software that comes with every Mac.
Whilst it's built around the scenario of making a song, lots of the tips and processes also apply to recording a spoken word piece.
It's a great place to start if you're new to Garageband and want to give it a try. They also provide a free template to use in the video description.