Covering a cake in marzipan uses exactly the same method as covering it in fondant. Stick the cake to the cake board with a small ball of marzipan. Now, take roughly enough marzipan to cover your cake. This can be hard to judge and is a matter of practise, so if in doubt always use more. Knead the marzipan a little, until it is smooth and pliable. Roll it out into a rough circular shape, about half a centimetre thick.
Once cooked, leave the cake to cool in the tin. When cool, remove from the tin and place on some baking parchment. Drizzle a couple of tablespoons of brandy (or your other chosen liquor) over the cake and wrap it up tightly in parchment and clingfilm or foil. Every few days unwrap the cake to feed it with another spoonful of liquor, then wrap it back up and return to a safe, temperate storage space.