Could any one tell me how to assign "template test" to existing Automation Test in QC

I know that one can assing template test to qtp script while creating new test in test plan, in my case i have to desing the tests to existing manual test cases other word i am not creating any new test just assigning automation test to manual test while assigning there was no option displayed to select template test

The reason why i am planning to create template test is
when i launch QTP through Remote agent default test settings are changing, inorder to avoid that i would like to assing all the test to a Template test

I am ok to implemenet any alternate solutions which solves my issue without using template test

I wonder if any one can help me