I've heard you can use the merkaba in differents ways.
-have a little crystal merkaba on yourself (pendulum best than pendant because the shape is more precisely cut), it's protecting your energy field.
-have a slightly bigger crystal or orgonite merkaba in your home to protect the energy of your home
-vizualize yourself inside a merkaba to protect your aura (you can vizualise motionless).
Some vizualise it moving from left to right, but better not go in the wrong direction it will have negative effects. Some do it with the 2 pyramid rotating in opposite direction but it is strongly inadvisable for a normal human being because it will move you into others space times and a normal human can't manage that, we are not enough evolved yet for that.