I think you are asking how to improve long term memory. The secret is effort, which won't surprise you. To remember something you need constantly to review the item, and to practise recalling it. You test yourself, and do this over a period of time. At first you do this after a very short period, and gradually increase the distance between such reviews.
So you would re-test yourself after a few seconds, then a few minutes, then hours, then days and then months, and then years. This is called spaced repetition. In addition, the practice of making yourself recall the information without a prompt will help firm the item in your long-term memory.
Learning new information and trying to place it into long term memory is more effective if we space the material out over time as we learn it. Meaning taking a longer spaced amount of time to encode the information.
