This means to direct the heart of the seeker towards the Divine Presence, where he will not see other than his Beloved One. It means to experience His Manifestation in all states. Ubaidullah al-Ahrar said, "The state of Awareness of the Heart is the state of being present in the Divine Presence in such a way that you cannot look to anyone other than Him."
In such a state one concentrates the place of Dhikr inside the heart because this is the center of power. All thoughts and inspirations, good and bad, are felt and appear one after another, circling and alternating, moving between light and dark, in constant revolution, inside the heart. Dhikr is required in order to control and reduce that turbulence of the heart.