On Windows or macOS you can simply use the built-in speech to text feature which comes with your operating system.

For Windows: To bring up the speech-to-text, just press the Windows key + H. This brings up a small window at the bottom of the screen and when you then click the microphone symbol to start dictating.

For macOS: You first have to enable dictation, you do that in System Settings->Keyboard in the "Dictation" section. Turn dictation On and then confirm that you wish to enable it. You can then also see which button enables the speech recognition.  This is usually a function key, for example on a MacBook Air it is the F5 key which has a microphone symbol above it. 

To use these features inside IdeaMapper, wherever you would normally type text, just activate the speech-to-text feature of your computer.