By popular demand we are going to try writing three-minute plays next week. Three minutes is about three sheets of paper, or about 5-600 words.You can find lots of examples of radio drama here:
Don’t have too many characters: one or two is fine. We might want to act them out. Read the examples to see how radio drama works. 

The examples also show you how a radio play is laid out on the page. You don’t have to do it perfectly, and will find it tricky if you are just using Word or similar, but give it a go. It is worth trying because any day now you may want to apply for one of the BBC’s writing competitions and if you don’t do it right they will chuck you out straight away. 
And remember, the prompt is ‘Dreams’. That can be interpreted in any way you like but should not be the title. 

For anyone who is struggling with how to indicate voice-overs etc, here is the BBC’s official template.
Voice-over is useful because it is another way of telling us a character’s thoughts without having a stooge they tell everything to. Ideally you don’t want either, but that gets tricky.