The checklists are prioritized lists of all the tasks that you need to carry out. They list everything that you have to do, with the most important tasks at the top of the list, and the least important tasks at the bottom.
To use your checklist, simply work your way through it in order, dealing with the A priority tasks first, then the Bs, then the Cs, and so on. As you complete tasks, tick them off or strike them through.
Mastering procedural processes and repetitive tasks with checklists allows you to focus on the larger goals at hand. It’s the minutiae of the workday that can be easily forgotten at the detriment of other important projects.
But in you’re in an operational role, or if tasks are large or dependent on too many other people, then it may be better to focus on a longer-term checklist, and "chip away" at it day-by-day. Many people find it helpful to spend, say, 10 minutes at the end of the day, organizing tasks on their list for the next day.