Sometimes you don't want to type. So why not record your voice instead?
Tap the + button
Click the Start Recording button
Wait for the countdown
Record your voice
Click Stop Recording when ready
Choose Use Recording
There may be a slight delay as the audio hotspot loads onto the page.
Book Creator for iPad
In Book Creator for iPad, the menu item says Add Sound rather than Record, but it works the same. You will also have the option here to import any music/sounds in your iPad's music library. Just tap on the Import from iPad link and it will open up the browser for your music library. When you choose something here, it will add it to an audio hotspot on the page. You can also use this sharing method to add sounds that aren't stored in your music library.
Giving permission to use the microphone
The first time you try to record your voice, your browser will ask for permission to access the microphone. You'll need to click Allow to continue.
If you're not asked for permission, or if something's not working, you might need to unblock the microphone for Book Creator to use.
In Chrome, go to Settings > Advanced > Privacy & Security > Content Settings ... and click on Microphone. If you find Book Creator is blocked, click on the trash can icon to unblock it - the next time you use Book Creator, you'll be asked for permission again.
For Book Creator for iPad, you can go to Settings > Book Creator to ensure that you have access to the microphone.
If that doesn't work, check here: Settings > General > Restrictions. You may have restricted use of the Microphone.