Feeling the same amount of excitement as a friend, when they tell you they're accomplished their goals.
Imagine you are a student and a friend in your class has just failed a major test or exam. Your friend is really upset, because she studied really hard and still failed. Even though you got a good grade on this test, you remember what it is like to fail, so you encourage your friend. You could say, "I'm so, so sorry about your grade. I know how hard you studied and how disappointed you must feel." and let them know they can come to you if they need to talk.
If someone is getting bullied at school, and you see this interaction. You demonstrate empathy by first, remembering what it is like to be picked on and how it made you feel. Then, you may stand up against the bully and defend the person or even help the person by being there for them when they need a friend. You could also show empathy by taking action by reporting the bullying to an adult.