Communication with the dead is an advanced level of openness. You should meditate on the third eye and open the astral senses.
Communication with them can also happen through dreams but they are not always the ones who communicate. It can happen that you want to talk to them so much that you dream it only out of pure desire given by the subconscious.
Otherwise, if you already have some opening of the astral senses you can try through the tarot if you know how to read them.
If you are an initiate I recommend you do the 40-day meditation, so as to start moving the energies, and do a lot of meditation of the void which helps to empty the mind, control the thoughts.
With time, and as soon as you are open, you will be able to do it I am sure. Don't give up if you don't see immediate results. Meditation, and this aspect, are slow as growth. It takes a lot of work and perseverance