you have to make sure the floor will support it first off. secondly you should install a bladder for the base to fit into and set the base into a mortar mix that will hold it firmly. it's not quite that easy but it isn't really difficult, you just need the precise instructions which is hard to give on here.
nightwork4. Thanks for your answer. Do need more inf. Can you write a hub with diagrams? What's a bladder? I was thinking of putting down hydrofugic (waterproof?) chipboard on top of floor boards and then just placing the shower base on top. My husband was going to replace boards with said chipboard and then just place base on top.