Hey Bob to open the microphone just long hold the button with the microphone icon and choose the microphone icon from the box that opens and you should be able to voice text. I haven't tried it myself but it should work. You could also choose from the same box that opens the the large T with a pen above it and that wil allow you to use the s pen to write messages. To change it back just choose the keyboard icon or long hold the button again and than choose the keyboard icon.
I hope this helps you.