Symbolism is a figure of speech to represent an idea in literature, an example would be a metaphor (comparing two different things without using like or as). When people say time is money they mean use your time and money wisely, because both do not last forever. Time and money are very different things, and it is an example of symbolism because these words represent an idea in literature while meaning something different. An example of using this is from Whodini's song "Fugitive".
'Cause time is money and money is time
You might waste yours, but I'm rocking mine
So rock on!
Hope this helps, now you know the answer and how to do it. HAVE A BLESSED AND WONDERFUL DAY! :-)
- Cutiepatutie ☺❀❤