Now your camera is on manual mode, you will also need to set your lens to manual focus using the AF/MF switch on the lens.
Now your camera is on manual mode, you will also need to set your lens to manual focus using the AF/MF switch on the lens. Then, if you have it, use the 'Live View' feature of your camera to display an image preview on the camera's LCD screen. Once you have done that, identify a bright star or a distant light source and digitally zoom in on that point of light. Once you've done this, adjust the focus ring until the star or distant light source becomes as small and sharp as possible.