the obvious easiest way is to by the tubes of writing icing

but...what you want is a royal icing style thing...can be done basically using an egg white, icing sugar and enough water so its still thick enough to hold shape but thin enough to pipe (practice on a plate 1st to make sure consistency is right)...there is other recipes using glycerol as well, but you can get away with just the egg white

you could also use butter icing tho, especially if theres any potential egg allergy sufferers...just one part butter/marg to 2 parts icing sugar...if you beat like h*ll in the mixer or with hand blender you can get it more than easy to pipe...and it will set quite firm if left in a cooler place (warmth will melt the butter)

I've just made my first proper cake as a dummy run for my little boys birthday in a couple of weeks but it needs finishing off.  I've iced it in the fondant icing but I want to do that piped icing that sets hard in squidgy patterns around the base and to write on the actual cake with.

Can anyone help me with a recipe & instructions on how to make this icing please?

Thanks in advance x x  x