To show empathy is to identify with another's feelings. It is to emotionally put yourself in the place at another. The ability to empathize is directly dependent on your ability to feel your own feelings and identify them.
If you have never felt a certain feeling, it will be hard for you to understand how another person is feeling. If you have never put your hand in a flame, you will not know the pain of fire. If you have not experienced jealousy, you will not understand its power. Reading about a feeling and intellectually knowing about it is very different than actually experiencing it for yourself.
Among those with an equal level of emotional intelligence, the person who has actually experienced the widest range and variety of feelings —the great depths of depression and the heights of fulfillment, for example, —is the one who is most able to empathize. On the other hand, when we say that someone "can't relate to" other people, it is likely because they haven't experienced, acknowledged or accepted many feelings of their own. Once you have felt discriminated against, for example, it is much easier to relate with someone else who has been discriminated against. Our innate emotional intelligence gives us the ability to quickly recall those instances and form associations when we encounter discrimination again. We then can use the "reliving" of those emotions to guide our thinking and actions. This is one of the ways nature slowly evolves towards a higher level of survival.
For this process to work, the first step is that we must be able to experience our own emotions. This means we must be open to them and not distract ourselves from them or try to numb ourselves from our feelings through drugs, alcohol, etc.
Next, we need to become aware of what we are actually feeling —to acknowledge, identify, and accept our feelings. Only then can we empathize with others. That is one reason why it is important to work on your own emotional awareness and sensitivity, that is, to be "in touch with" your feelings.