I'd recommend you do a search through the Microsoft documentation to get
the official instructions, but generally, this is how you would do it:
1) Create a new project workspace using the Site Settings functionality.
*DO NOT* create the workspace by creating a new project in MPP. It is important
that the workspace has not been associated with a project.
2) Add your list to the site.
3) Save the site as a template into the site template gallery.
4) Download the .stp file to a local drive.
5) Run the STSADM addtemplate command to register the new template with Project
Server
6) Go into the Project Server Settings, Workspace Provisioning Settings,
and set the default template to your new template.
-A