How can I use other person natal chart to gain information for that person and help me in spell toward this person ?
Learn astrology. Particularly Horary.
I mean you could use it as a fetish link? I mean its basically the details of that person at their birth.
Any physical representation or symbol of the link(target), can be used through contagion magic or sympathetic magic. So yes, a chart could be the symbol of the target. Working anything on that I’m sure involves Horary Astrology and/or Planetary and Elemental Magic.