Parents can help their child understand their emotions simply by talking to them about how they feel, labelling the feeling and all the associated bodily responses that come with it. For example, if they feel jealous, it is great to make them aware that this feeling is one that is felt by everybody, including adults and that we all feel the same sorts of feelings when we feel jealous. Giving control back to the child is empowering for them, they can see that it is normal to feel this way sometimes, but that there are ways to minimise the negative emotions they are feeling. This can also ground them and have them feel more confident.
People think of emotional intelligence as something you only need as an adult or at work, but this is definitely not the case. Both of my children were educated in emotional intelligence from the age of around 6 so that they could not only recognise their own emotions but that they could also recognise emotions in other children as well. They were always streets ahead of their peers in this regard and I would do it all over again as I have seen all the benefits this can give your child. So emotional intelligence for children is incredibly valuable and will assist your child in many ways. Successful leaders in the future will need to have high EI so I highly recommend you investigate this valuable input for your own children.