Inspect the sheathing on the floor. Check for gaps and cracks. Open a tub of dry set mortar and mix it with a trowel. Turn the Hardibacker upside down.
Spread out the dry set mortar with the trowel over the entire back of the Hardibacker. Dip the trowel into the dry set mortar as needed and spread out the mortar 3/32-inch thick across the back of the panel.
Line up the Hardibacker at the bottom corner of the room and press it firmly into place by hand. Run your hands over the entire surface. Line up the first Hardibacker nails at the bottom corner of the panel. Space the first nail two inches from the bottom.
Hammer the nail into place until the head is flush with the top of the panel. Insert screws every eight inches over the surface. Keep the nails 3/4-inch from the edge of the panel and 2 inches from each corner. Hammer all of the nail heads flush with the top of the panel.
Butt the second panel up to the first. Leave a 1/8-inch gap for expansion and install this panel and all of the remaining panels just like the first was installed.