Yantra is a certain energetic form of a divine, created towards a specific purpose. It is a corridor or a channel to a particular divine quality, divine being, dimension, Deity, or God. Yantras are used in spiritual practices as they benefit focus and aspirations towards the Ultimate. If you place a yantra or a few of them in your home or office, you'll notice that the space itself becomes vibrantly alive.
It is so indeed because, in a way, yantra is a channel that connects your living space with the Ultimate, with the Source of Life.

Mandala is a configuration of geometric forms and symbols aligned with the Universe or Cosmic geometry if you want. Mandalas represent divine, natural harmony. They are widely used for meditation practices and in spiritual life.

If you decide to place a mandala in your home, you will benefit from its energy of balance and order. Your home will be a way more potent place for recharging and refreshing. If you keep it in a place for meditation or spiritual practices, you'll make the space conducive to mental alertness, focus, and high frequencies.

This will deepen your experience and will help to progress in your spiritual growth. If you keep one in the office, you'll notice the upsurge in your creative energy and dedication to your work. You will be facing way less friction, achieving the desired results.

Every mandala and yantra holds an energy imprint. You can benefit from it in a simple way. Keep a yantra or a mandala in a quiet space, sit in front of it and focus on it for 5–20 minutes daily. Just observe it, think of it, try to mentally grasp it in its totality, and discover the feelings you encounter when you are in touch with it. Do this every day for 40 days. After that, you'll imbibe the energetic form, and whenever you need to boost your energies, close your eyes and invoke a mandala or a yantra in your mind. Feel the energy that comes out of the form and flows into yourself.