Ah, you can do it. Just set the camera for manual adjustment of everything---probably a big M on the control dial---and then adjust ISO, apterture (f-stop) and shutter speed to be the required values. You need a long shutter speed to increase your chances of capturing a flash/bolt. You need lower ISO settings cause lightning is damn bright and you're collecting a lot of light over a long exposure. You'll also need to pick a fairly large aperture (f-stop) cause you want a pretty wide depth of field.