How do you find a ghost?

People as a rule don't go looking for ghosts. If you are intended to see one a ghost will find you.

However if what you're really asking is how do you find or "see" a ghost that you are currently experiencing or are sharing "space" with, that is a different thing entirely.

I do not recommend you dabble in this if you have no previous experience.

There are people who can and will help you to contact; understand the needs of; and remove ghosts.

Let the experts, including the representative of your own faith system, help you.