Have to try to look 'through' the magic eye poster, pretend its a window, don't scan it looking for something to popup cuz it won't. Also helps if the poster is big, at least paper sized, looking on a tiny phone screen might not work too well. Also, if your depth perception isn't good maybe try another illusion, since you may not be able to solve magic eyes.

CW: Be ware if you have any motion visual issues like seizures, migraines, motion sickness etc, but the following site has all sorts of illusions