Add it! -First you've got to decide if it's an idea people need to vote on, or something they can pretty much do on their own. Because that's what decides if your idea should be a "Proposal" or "Idea" post.
If it's a proposal, it's treated like a "bill" for people to vote on. So in example, you could type in the name of a city, (or social movement), and see all the proposals/bills that people are proposing. Needpedia obviously can't endow these "bills" with any kind of legal power, but groups can use these tools to put ideas to a vote. -And help us make Needpedia better by sharing their ideas for problems with it.
If it doesn't need to be voted on then it's simply called an "idea" post. And idea posts are organized based on a problem they're based on. The main reason for this is that if you have a problem, you want to know what all your options are. -For that one, specific problem. Whereas if you're in an area, (or especially into a social group or something), you want to know what people *there* are proposing. -It's also handy having the ability for "bills"/proposals to address numerous problems and ideas at the same time.
If you have an idea for a problem that's not listed yet, you'll need to create that problem post first. -It doesn't have to be more than a few sentences though, because Needpedia's all about solutions.