Android: To add a subtask to a task, simply tap on a task, then tap on the 'Subtasks' . From there, you can either enter subtasks in the text box, or use the mic to speak your subtask and tap the enter button orto save it. iOS: To add a subtask to a task, simply tap on a task, then tap on 'Notes & Files' . From there, you can enter subtasks by typing in the text box, and clicking. Web, Mac, Chrome: Click on a task and the task quick menu bar will appear. Click on 'Subtasks' and then 'Add a Subtask' and type in your text. Press enter when it's complete.