Put the IDETemplateMacros.plist file in the correct location. It could be placed in one of five locations, depending on the range it needs to cover.

• Project user data:
  <ProjectName>.xcodeproj/xcuserdata/[username].xcuserdatad/IDETemplateMacros.plist
  using that location would cover a specific project for just a single developer.

• Project shared data:
  <ProjectName>.xcodeproj/xcshareddata/IDETemplateMacros.plist
  using that location would cover a specific project for the whole team using the workspace.

• Workspace user data:
  <WorkspaceName>.xcworkspace/xcuserdata/[username].xcuserdatad/IDETemplateMacros.plist
  using that location would cover all projects in the workspace for just a single developer.

• Workspace shared data:
  <WorkspaceName>.xcworkspace/xcshareddata/IDETemplateMacros.plist
  using that location would cover all projects in the workspace for the whole team using the workspace.

• User Xcode data:
  ~/Library/Developer/Xcode/UserData/IDETemplateMacros.plist
  for all projects edited by the local user.

That wide location choice is useful if you work on multiple projects with different header conventions or you want to share a default header comment format with other team members.

Reference

Text macro format reference

Text macros reference