Click on the ellipsis and select 'Enable phases'. You will see the stage rows are now indented to the right and under the phase you enabled.

Click on the phase name to change it.

You can add additional phases by clicking on the '+' icon on any phase row you have created.

Type in the phase name and click Add. This will create the new phase under your last stage. You will then need to reorder your stages and tasks if you need to move them under the phase you just created.

To add a stage click, hover over a phase or stage and click on the '+' icon.

Type in the stage name and click Add. This will add a stage under the last stage grouped within this phase.

To add a task to a stage, hover over any stage and click on the '+' icon.

Type in the task name and click Add. This will add a task under this stage.