Is it similar to how people today believe astrology? As in X sign means you have X personality, or the future of the person who has X sign, and so on.
How similar is modern astrology to astrology as practiced by the Ancient Greeks? by u/Asinus_Docet is a very extensive and detailed write up that touches on some of your questions. It does not delve too deeply into the specific of how it was used, but does discuss it briefly.