Ask short questions, the answers of which will be yes or no.
Wait for them to answer you, find out if they are close to you.
Just be warned that it is not for the most sensitive, this can be a terrifying experience if you have never touched a device before, so we recommend that you research the phantom box before deciding to try one for real.
Use at your own risk, I cannot be held personally responsible for you or any result (paranormal or not) of using this app!