To link phases to milestones check the option for Phases - Based on milestones as highlighted in the screen shot above. Phases will be adjusted to adopt one project phase per milestone with phase text the same as the milestone task description. If a phase is deleted then tasks previously assigned to this phase will have no phase assigned. With this option there is no need or possibility to define phases independently of milestone tasks.

To define phases separately check the option for Phases - Define separately and then click on the Edit Phases button or link text as shown in the diagram above. Click here to learn more about defining phases separately.