As with any intentions/manifestations, besides always being in the Heart Space, be sure to always state your intentions in a positive manner, vs a double negative i.e. "I don't want a crappy car"
Once re-activated, the MerKaBa becomes a tool; it is a part of your consciousness. This tool will protect you from Electromagnetic Frequencies, for instance. I suggest that this be one of the "programs" or intentions that is set into the MerKaBa Field.
To set a program, or intention, into the MerKaBa, you need to be in the Sacred Space of the Heart. As stated earlier, when you create from the Heart Space, you are creating what is for the Greatest good of everyone as all Heart Spaces are connected. When you create from the Head, you create in Duality.
Visualize the MerKaBa Field around your body (perhaps just seeing the one Star Tetrahedron that is solid and stationary) and "send" in your intentions. It can be as simple as that. If needed, you can visualize a ball filled with all the Highest Aspects of Love and Joy, for instance, and watch as it pops and flows onto your MerKaBa.
As things come up during the day, you can stop, go into the Heart Center, and set your intentions.
Click on the button below for a simple exercise to use for Clearing your Field