Repeat this over a few times. You may not feel much at first, but with practise you will feel a tingling surge of energy like adrenalin and a fluttering or pulsing under your skin as you do this. Even if you don't feel anything you are still raising some energy. When I first started using my chakras, many years ago, I didn't feel anything happening in them for several months. Many people report feeling some sensation in them the first time they do this.
Some people seem to have more natural chakra activity than others.
The heart chakra merits special mention due to the odd sensation it causes. When it activates fully it will feel as if it is racing at a seemingly impossible rate. It is a powerful sensation. Ignore this when it happens, it won't hurt you, it is not your heart racing but the chakra working. Tap your fingers on your chest, in time with your heart.