In Al-Mesbah of Kaf'ami, there is an instruction about seeing dead relatives in your dream. The instruction is as under: "It has been mentioned in some books by Imamiyah scholars that if a person wishes to see a vision of the Prophet (s) or of the Imams (a.s) or his parents or someone else in his dreams, he should recite certain Suras such as Al-Shams, Laylatul Qadr, Al-Kafirun, Al-Ikhlas (Al-Tawhid) and Ma'uzatayn i.e. the two suras which begin with A'uzu (qul a'zu bi-rabbinnas and qul a'uzu bi-rabbil falaq). Then he should recite Sura Ikhlas (Al-Tawhid) one hundred times and recite Salawat one hundred times and sleep on his right side while he is in the state of Wuzu. He will see whomsoever he wants in his dream, and they will talk to him and will answer his questions.
There are other instructions in the same book which you can refer and read for yourself.
It should be noted that there are narrations from the Infallible Imams (a.s) reported in our narrative sources about seeing the Messenger of God (s) in a dream. As for how one can see others in a dream, we could not find any reference other than what has been quoted from some Shia writers in Kaf'ami's al-Mesbah.