Inspect the block on the inside of your house and verify it is not damaged at any location. Move from one side of the house to the other and check to see that there are no gaps or cracks between the blocks before turning the heater on. Repeat the process for the block on the outside.
Slide a tube of silicone sealant into a caulk gun and lock it firmly into place. Cut off the tip of the sealant with a utility knife at a 45 degree angle and press the trigger to release the sealant over any cracks on the inside or outside of the house.
Move around the entire house and cover up all of the cracks with the silicone sealant before turning the heat on. Inspect the insulation in your house and verify it is installed against the cinder blocks, particularly in the attic and upstairs areas.
Adjust the thermostat to the desired setting. Turn the button to "Heat" and the fan to "Auto." Move the temperature to the desired location and let the furnace heat the house.