You've set up your project and configured your systems. It's time to prepare the backlog of issues that your team will work from.
A backlog is simply a list of features, which could be for your product, service, project, etc. These features are not detailed specifications. Rather, they are usually described in form of user stories, which are short summaries of the functionality from a particular user's perspective. This is a common template for a user story: As a <type of user>, I want <goal> so that I <receive benefit>. For example, "As a developer, I want to log time against my tickets in the issue tracker during a sprint, so that I can show my progress."