Here are the steps to plaster a ceiling:

1. Prepare your work area by covering your whole floor with a few large drop cloths.
2. Remove any nails or screws from the ceiling.
3. Mix up your plaster.
4. Skim coat the ceiling with plaster.
5. Apply a second coat of plaster.
6. Trowel up the plaster.
7. Final trowel.

Here is a more detailed guide on how to plaster a ceiling . I hope this helps!