In Sonar start a new project. Add what you want to it as far as audio tracks or Midi trks.
Set all your options the way you want or leave them as is.
Go to File/Save As and it will bring you to a new window. There you can choose what to save you project as in the 'Save As Type" feild under the name you will give it. Template should be the second choice.
Then choose where you will save the file.
I would do as Larry suggests and direct Sonar to find this file you just made in the 'Templates' field