I should've been born in the times of Annie or A Christmas Story, where people didn't have TV and used to just sit around and listen to stories acted out on the radio. Because when I write a story, I hear the conversations in my head and that's what gets written down! I have to go back through and add the details later, and descriptions are so much harder for me! I've heard the opposite, where some writers are great with descriptions and when it comes to the dialogue, they struggle.
If you find yourself in the same situation, my best advice for changing your radio script into a novel or short story, or a story in general is two things. Add setting, and add senses. Charlotte Cook, who edited my first 20 pages, suggested I tag the dialogue I had. So here is an example of tagging from a conversation I actually heard my characters have while going to sleep last night. (Another good idea is to keep a notebook by your bed because I always get inspiration as my mind is clearing itself at the end of the day!)
Talon is cleaning an animal. I haven't decided what yet. Fish? Probably. And Kiana is watching him.
"You do know that's disgusting."
"News flash, Kiana. This is what you look like on the inside."
"Yeah, but no one's going to eat me."
"That you know of."
"Is it possible? The rough-necked Talon can actually make a joke?"
He smeared blood on my hands.
"Is it possible the stubborn beauty can get her hands dirty?"
"Beauty, huh? Don't take it back now, I heard you say it. Come on, admit it, you think I'm beautiful."
"Beauty isn't real, Kiana. It fades like the seasons."
"Yeah, but while the summer's hot, it's hot, right?"
Okay. So even though it's just words, fill in the spaces between. Add the trees, since they're outdoors. And the weather. Is it cold? Scorching hot? Then character movements. Talon's probably holding a filet knife, and Kiana is twiddling with a long blade of grass. Does he smile at her? What is she thinking? You get the idea. Here's what tagging the dialogue would look like:
Talon's knife sliced through the fish's underbelly. I caught a glimpse of red and turned away, my stomach churning.
"You do know that's disgusting," I said.
"News flash, Kiana," said Talon. "This is what you look like on the inside."
How would he know? "Yeah, but no one's going to eat me."
"That you know of," Talon added under his breath.
My eyebrows rose. "Is it possible? The rough-necked Talon can actually make a joke?" A bird chirped in the tree above.
Talon slid a look at me, then darted out and smeared his bloodied hands on my fingers.
"Ew!" The slimy wet reeked. I went to wipe it on my jeans, but it would probably stain them. Yuck. What a low blow.
He hit me with one of his rare smiles. "Is it possible the stubborn beauty can get her hands dirty?"
The corner of my mouth lifted. "Beauty, huh?"
Talon opened his mouth, his brow hardened and then he stared at the silvery skin he was peeling from the pink fish meat within.
"Don't take it back now, I heard you say it." Was that color coming to his cheeks? "Come on, admit it. You think I'm beautiful."
He kept his head bent. "Beauty isn't a real thing, Kiana." His head lifted, his eyes were too serious, almost as if they were being forced. My smile stretched. "It fades like the seasons."
Nice try. "Yeah, but while the summer's hot, it's hot, right?"
His mouth twitched, hiding a smile.
Anywho, that's very rough, but it's just an example. Hope it helps!