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… you have a project/product you want or need to get done with a definite goal.
Progress in a project needs to be achieved as best possible, and knowledge and risks about the work to be done need to be addressed as soon as possible.
Therefore, create a cross-functional, self-organizing team, that gets facilitated by someone experienced (the ScrumMaster), and that has enough competencies to accomplish the project.
Once you have such a team (Scrum Team), you are ready for a Sprint and your next step is a Sprint Planning Meeting.