Actually everyone will not have the same size of both eyes. There must be the little difference in size. Thus, it is normal and there is no need for you to get worried. You just let them go. If the two eyes have great difference in size of both eyes, you could go to the hospital to accept the surgery which could let you have the same size of two eyes.
You can do some different in your smaller eye. you can use white eyeliner in the waterline, which can open eye up and makes it look bigger. If you want your eyes to look longer, you may use maybe a little eyeliner on the smaller eye. You can enlarge your eye by making up eyelash by curlling your lashes on the smaller eye.
It seems that your eyes are not exactly identical to each other. However, as far as I know, there are simply no natural ways to change this, unless you try to do some cosmetic surgery to tackle this proble, but there are risks and side effects. My advice for you is to wear sunglasses whenever you go outside and leave a long hair, maybe this helps you to cover your defect.