To use the voice feature, simply start creating a new task by tapping on the bottom right corner of your screen and select Task . You will then see the microphone icon in the top right corner of the screen (within the text box). Tap on this and wait a few seconds and start talking. After you finish talking, tap on the blue check mark on the lower left corner. You will then have the option to add this task to a specific list and set a reminder. Once you're done with the task, tap on on the right corner and you're done!
On iPad, tap the floating action button and then proceed as directed above. The press and hold feature works with this button as well.