To be fully present is quite simple, but not always easy. It takes commitment and practice. Our minds have a tendency to drift anywhere other than right here, right now. Being present means that your awareness is fully in the moment you are in. You are not worrying about the future or thinking about the past. The present moment is where your life is happening at any given time. The past is an illusion. The future is an illusion. The past no longer exists, and the future never exists. They are simply concepts. All that is real is whatever is happening now.
To cultivate your ability to be present, start by practicing being a witness, not a participator, of your own thoughts. One of the best techniques for this is meditation. Another is self-hypnosis. Or you can just tell yourself that you are not your thoughts, and imagine them passing by like clouds. If you give your thoughts your energy (attention), they will tempt you to go back to living in the past or future.
Focus on whatever you are doing in this moment. Keep your thoughts and actions on the task at hand. This could be feeding the dog, brushing your teeth, putting laundry away. Keep your mind focused on now vs. memories of the day behind you or the time ahead of you. Simply be in the moment.
This simple shift in focus from what is an illusion to what is here and now, will make a profound difference in your experience of life. The time to start is NOW.