Because you are under 18, you cannot decide where you will live. When you apply for asylum the Migration Agency will contact the social services in the municipality where you are. The social services are represented in every municipality. Their staff works according to a law called the Social Services Act. The Social Services Act is about everyone in the municipality's right to care. It contains rules for how society should help everyone who needs help. It is the social services who will decide where you live.
If you have relatives in Sweden who you want to live with, the social services must agree that you can live there. If you don't have relatives in Sweden who you can live with, you can live with a family or in special accommodation. The social services can help you with this. You won't be able to choose a place and you may have to move to another place while you wait.