The result is that the longer you expose the film to the target, the more light it collects which will eventually show up in the form of a picture. For example, the same film may require an exposure setting of a fraction of a second for a picture of the moon, several seconds for an image of Saturn, and an hour or more for an image of a galaxy. Armed with a camera that accepts adjustable exposure settings, the next thing is to determine what you want to photograph. There are many options available including star fields, constellations, large open clusters of stars, sun settings, moon settings, aurora, eclipses, and much more. For most of these types of pictures you will need a way to hold the camera steady during the required exposure.
Most photographers use a tripod to which the camera can be fixed.
If you have access to a telescope you may be able to attach the camera to the outside of it. In a desperate case you might prop the camera up using rocks. The reason is that no matter how still you think you can hold the camera you will shake or move slightly and that will ruin the image. Jiggling the image just a fraction spreads the photons out to adjacent and further locations on the film plane. That means that the film begins to remember the light in a new place causing a blurry image.