Here's how you do it:
Visualize a big, bright orb of light above you, and pray to the Light to protect you completely. (It would help to repeat a prayer or a mantra while doing this exercise. If you are not used to praying, a simple chanting of OM is powerful enough as well).
As you pray to the Light, the orb bursts open, and a downpour of golden-white light comes down upon, through and all around your physical and etheric bodies. If you cannot imaging a golden-white, accept whatever colour comes to you; it is the right colour for you.
Visualize the Light now solidifying all around your energy-field serving as an invincible barrier against all negative energies and dark forces, giving you complete protection.
Initially while you are new to this exercise, you may want to remain in this Light until you feel you are completely protected.
Finally affirm that you are now safe and protected, and free from all evil influences around you.
Thank the Light and God.
Once you are used to this exercise, you can draw the protection of Light around you instantaneously.
You can use this protection to protect anything - your house, your car, family whatever. It works!