If you mean Ricinus, that's an annual anyway and is best raised from seed if you don't want to buy a plant in Spring.
If you mean Fatsia japonica, the usual method of propagation for that is seed or semi ripe cuttings in early summer. Even were leaf cuttings possible, that leaf would now be too old for those purposes - leaf cuttings are done immediately the leaf is severed from the parent.

Thank Bamboo, I thought that would be the case. As I am a complete novice I thought I could be wrong.

I will just buy one.