The simplest way to become familiar with the energy of Kali is to put an image of her on your altar and look at it from time to time, imagining her qualities. (You could also use a Kali mantra; however, it is important to "receive" such a mantra from a teacher. Many experts say not to use mantras of the strong goddesses without having them empowered by a teacher.)
Find a picture of Kali, preferably a detailed and beautiful one. Look at the image, noting her beautiful face, her wild hair, her upraised sword. Look at her necklace of skulls. Notice the emotions that come up as you look at her. Notice especially such charged emotions as fear, excitement, aversion, confusion, or attraction. Ask the universe to help you experience Kali's love.
Once you've become familiar with her visual form, take a few moments to meditate on her.
Imagine Kali sitting before you. Feel that an energy of blessing filled with strength, love, and wisdom arises from her heart in a stream of blue light and enters your own heart. Feel that Kali's blessings purify your heart of fear and anger. If you like, you can imagine her drawing those negative emotions out of you and dissolving them like smoke. Feel her blessings coursing through your body, opening you to strength, enlightened clarity, and love.
Fold your hands in Anjali Mudra and offer thanks.
To read more about Kali see "How to Be Fierce."