SharedPlan Pro is a project management tool for the Mac. It is also available for Windows and you can access the program's data via its web app, if you are on the go. If you follow the quick start guide that is shown to you when first launch the app, you will be able to start using the problem with no problems. But it is hard to jump at it right away without looking at this quick start guide, at least it was for me.
To create a new task for your project, all you have to do is double-click on the canvas (the background) or simply click and drag it. The task will appear as a white rectangle or square, depending on the shape you give it. This is nice, because you can make big rectangles for more important tasks and smaller ones for less important tasks. You can edit a task by double clicking on it. Here, you can assign a task a priority, a cost, delay, a planned deadline and an actual deadline. You can also add a few notes about it and assign different people for it. SharedPlan Pro will estimate the completion percentage for you when you add information about it while the project is underway.
There are different ways in which you can add tasks and manipulate them, and the quick start guide and the provided help cover this in detail.