After creating a Milestone Template with your defined set of Milestones, the final step is to create either a Salesforce Flow or an Apex Trigger that fires when a record is created. Please refer to one of the below articles depending on the preferred method.
Initiating Milestone Creation Using Salesforce Flow
Initiating Milestone Creation Using an Apex Trigger
Note: For any objects that are NOT Account or Opportunity, you will need to add a lookup field on both the Objective and Plan Summary Objects that point at your desired Object.
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