There may be instances where you may want to apply a template to a Project after it has already been created. You can apply a template to blank Project (where the Project does not contain any tasks) or to a Project that already contains tasks.
When a template is applied to an existing Project (where Project has already been created), the following are applied from the template to the Project:
However, Project Settings on the Template are not copied to the existing Project. This includes the options found in the Project Settings page (start/end of working day, timezone, weekends as working days, send task notification), Project View Settings (columns displayed, column order, column widths) and non-working days/weeks. For more information on what gets inherited from templates depending on when it is applied to the project, please see Project Templates - What Gets Inherited.
Please Note: The behavior is different when a template is applied during Project creation. When you choose a template while creating a new Project, the Project Setting (except for Timezone) from the template are carried over to the new Project as well as the Project Status of the template.
This help article provides step-by-step instructions on how to apply a template to an already existing Project.