yes it's possible. it's like being able to do art, while some are born with the skill, most will have to learn. however, there are still those who will never be able to learn. seeing spirits is the same way, sometimes it just takes training, other times the person is born able, and there are those who will never see/sense/hear them. these people however, might be able to see other beings like demons or astral creatures though, everyone's different.
to start, balance all your chakra's, don't just focus on the third eye, the energy needs to flow equally through your body. after that there's some simple exercises to increase your clairvoyance. third, before try to work with spirits, have some tea that increases psychic awareness. speak with your doctor first to make sure you're not allergic or the herbs you used aren't poisonous. don't get discouraged if this process takes a while, it's not an overnight thing.
final point, the veil between our world and the spirit world grows thicker and thinner throughout the year, as well as each spirit goes through times of active and inactive. the best time to try speaking with a spirit is around Samhain and Beltane. [i've noticed] not all will fall into this pattern, but this is the best time to try since the veil is at it's thinnest point on October 31. [also, do not use a Ouija Board. if you feel you need a tool, a pendulum is safer.]