This article provides detailed information on how to add a Content Type to SharePoint.
1. Select the "Gear Icon" and then Site Settings
2. Select Site Content Types
3. Select "Create" or to edit an existing Content Type, click on the Content Type Name.
4. Enter the Name of your Content Type, Select the Parent and Select the group to add it to.
5. To assign a template to the content type click on the Content Type Name
6. Either upload the template or enter the URL of a location in SharePoint. We like to enter a location in SharePoint to allow permissioned users to edit the templates as needed.
7. Select "OK"