Any book that you creat you can now add audio files.
On the far right of your screen in Bloom there will be three short bars near the top. If you click this, it will open an area with all the buttons to record someone reading the words on the page. You will record different files for each page of the book.
This is really only useful for electronic publications of your book. However, the advantage is that the read can hear the page read to them and then try themselves to read and pronounce the words. The sentence on the page is highlighted as the narrator reads the text. If you take the time to segment each word, the highlighting function will progress with each word as it is read. Make sure to use good audio recording equipment and have a skilled narrator(reader). If you do not have audio recording equipment, your computer can record the narrator or you could use a cellphone. Many places of the world are not yet literate in reading text, but their cultures pass down stories orally. This recording option opens up the world of written text to people that will never have formal education offered to them.
With the proliferation of electronic readers and cellphones, this is a great option for literacy in developing countries. All your electronic books can be used in Reading App Builder, another SIL software for creating a cellphone program for reading.