Managing Milestones in the Project Milestones Inspector
The name of your milestone as it appears in the outline; changing the title of your milestone here, updates the outline. 
The date of your milestone. Just like with names, changing the date here updates the outline. 
Show a critical path to your milestone, and assign it a color so it stands out. 
Adjust the slack limit for your critcal path; the slack determines how much the project can fall behind without impacting the deadline.