If you use GUIDE and double click your text edit box you'll bring up the property inspector. In there you'll see a callback for the key press function. Click the icon for that to go to the code for that. In there, get the text from the edit box and do something with it, such as display it in a static text label:
editTextString = get(handles.editText, 'String');
set(handles.staticText, 'String', editTextString);
