First, you learn about the basics of manual testing, becoming proficient in this aspect as it is the basis for all automated scripting.
Then you work with your company to obtain a legal copy of the application and schedule time with their representatives to determine the tool is the best fit for your needs or not.
The Tutorial would be stepped through at this stage for you to become familiar with the most basic of tool operations.
Attending the specific training courses for the tool you choose would be next on the list, as well working to find a mentor on the tool to help you along the way.
With those items covered, you'll then be able to write a test script.
Now some questions for you:
Why have you chosen WinRunner?
What experience in QA do you have up to this point?
Is your company currently evaluating WinRunner, or has it already been brought in and you are tasked to learn it?
Have you approached your management to let them know you might be needing formal training?
Insanity: doing the same thing over and over again and expecting different results