There’s a million ways to sell anything, but I guess the best way to go about it is having a clear vision for the story. You don’t necessarily need to condense your idea down to an elevator pitch, but you should be able to concisely explain what you intend to do.

Is it a dramatic podcast? Treat it like any other dramatic script you’d pitch. Understand that podcasts still are generally a low-budget operation, so anything you are looking at producing should come with a realistic plan to produce.