Use Emotion words frequently- some words you can start with are mad, happy, sad and angry. Every time the child is going through that emotion, use the word and emphasize it. For Example “Are you mad?” or “Did you get mad because ______(use name) hit you?”
The more you use that particular word, the more your child will get familiar with the word and start using it. You can also emphasize the expression of the emotion on your face to get the child to understand more about expressing themselves non verbally.
You can also talk about the characters in a short story and how they felt. Another idea is to model talking about feelings by doing it yourself.
Finally, when your child does use a word to express his/ her emotion, make sure that you respond accordingly and help them deal with their feelings. Help them to realize that sharing their emotions is a good and positive thing.
Just remember that all children take time to start talking about their feelings and it does not happen overnight. However, by using the words frequently, and talking about them, we teach the child the words so that they can use it whenever they are ready to.