You want star trails. Right?
Try to point the camera more toward the north. (Assuming you live in the norhtern hemisphere. Otherwise south.)
The closer the camera points to Polaris, the north star, the star at the end of the handle of the Little Dipper, the more circular your star trails will be. I assume that's what you're going for because that's what people often want.
The farther away from the north you point, the more the star trails become arcs until, if you point due east or west, they'll be almost straight lines.
Other than that, do what NB23 says. Put the camera on a tripod and lock the shutter open for a while. There's not a lot to it.
Do expect a bit of trial and error but, try it a few times, and you'll get the hang of it.
What the hell? it's only film. Right?