Milestones are located at the top of the roadmap.
There are two ways to create a Milestone:
Click on the green diamond shape that appears when you hover your mouse on the Milestones row.
Click on the + button on the Milestones row
Once clicked, an editor dialogue is opened to create a new milestone. Now, add details for creating a new milestone. Details required are:
Milestone name
Start date
End date
Milestone color