When creating a project, you can select one of the example Colour Policies shipped with the application, use a policy you've previously exported, or copy the policy from one of the listed projects.
All of the components of a Policy may be edited individually from within the Colour Management Preferences. However, if you need to completely replace the current settings with another Policy, you may do that by editing the project.
Note that when you create or edit the project, the files that comprise the chosen Policy are copied into your project directory (overwriting any existing files). Since the project settings use a local copy, any changes made to the source presets will not have any effect on existing projects.