This part of Tanya explains about G-d being one. The Rebbe asks: The Torah says that G-d Commanded the Jews to love him, but how is it possible to love something if you don't?
The Rebbe Answers that it's talking about the love for God which is hidden by every Jew, and you just need to reveal it. The way to reveal it is through thinking of G-d's greatness and what He does to us, and that He is our father and our life. The Torah commanded us to think of this in order to awaken this hidden love.