Build your project in Microsoft Planner by creating Buckets for Milestones.

Add a Bucket by selecting the 'add a bucket icon' at the far right of your screen.

From there is is very easy to add tasks under the bucket.

Add detail to the tasks

• Assign the task to people who will work on it. Planner will already have the names of everyone on your team. People must be assigned to the team in order to appear in the assign ownership menu.
• The bucket is already assigned.
• Update task progress.
• Identify the priority.
• Update start date and due date.
• Add notes for people who share the task. Check 'show on card' if you want the notes to show on the card which appears on the project board.
• If you have multiple items, you can add a checklist so that the individual items for this task must be complete before the entire task can be completed.
• Feel free to update with attachments and comments for your team.
• Once this task is created, the tool will track progress and let the team members know via email if they are close to the due date for this task.
• It is easy for teams to collaborate on tasks.
• It is useful to review this during the team meeting and update status, or add new tasks, live during your team meeting.

Here is an example of the project BOARD, where you can see the milestones (buckets) and tasks on one page.