It's important to understand what the idea is essentially. For example, think of a basketball stadium; you understand what it could be because it already has a defined existence. Similarly, your idea needs to have a real-world implication. Another example: think of Google. The idea was a search engine, but now Google's idea is organizing information.
To be able to use the idea that we understand, it needs activation. The idea you have may have applications in various situations. These situations are breaking because there is no solution or the needs there are unmet. We hence define the problem that the idea could actively solve. This is also called your first or set of first use cases.
Once we have a problem that people would pay to solve, we have to understand how it can be solved, how it is currently being solved, whether there are existing competitors, and what you could do differently but in a better way. You might already know a solution, but is it fit for selling? Can it be built and sold profitably? Will there be enough demand? These questions tell us what we need to do in order to make a solution.
Once we have approached the problem and can view it as it is under microscopic precision, we can apply our problem-solving skills to brainstorm or apply existing methods of solving to come up with a lot of solutions and ideas. Most will not be right. Through our experience and your preferences, we will come to a conclusion on what solves the problem given our newly built-up knowledge.
Getting to a solution was feasible, but can it be built into a product with existing capabilities? We can think of teleportation as a solution to travel, but such capabilities don't exist today. Similarly, thinking of a solution and building it with the tools and capabilities we have is an entirely different proposition. We will keep this in mind while we do the initial process as well. From this, we will design a product that can be made tangible.