To do this, start by defining the Milestones. Click on this tab in the left navigation bar:

Then, in the Milestones grid, define the start and end data of each stage of the project:

Now click on your project in the project tree and you will see the Milestones laid out in a Gantt chart:

When you enter new artifacts, specify which Milestone they belong to (here called Events):

The Event for each artifact is shown in the grid:

You can filter the grid to show only artifacts from a certain event: