"put the icing on sth", What does this idiom mean? Please explain to me and give example. Thank u.
I would change that idiom slightly to make it into:
Put the icing on the cake.
Your suggestion is not really an idiom, whereas put the icing on the cake is.
It means to finish something perfectly, or add the finishing touches.
Sometimes it can be used in the following way:
Well, that puts the icing on the cake.
Here it is being used sarcastically, it means that something got even worse, so be careful of this sarcastic use of the same phrase!