Since you have been doing black box testing so you know what testing is. So now all you need to do is look for the tool that you would like to learn and learn it’s programming language….Start with the record and play to get a feeling of it.. Use the online help books, for that tool, and qaforums.com, and you are on your way….I know there’s a lot you need to look for latter on but this will get you started..
Start with the record and playback feature of the automated tool. When you have finished recording a script you want to playback, look at the script/code that was created and analyze it. See if you can find the areas where you performed a mouse click, or a keyboard entry. By doing this, you will get an understanding for the code.
The easiest way i have learned the Win runner is take the printouts of Tutorial, read them thoroughly and practice the step by step procedure for recording the sample application(Flight Reservation) supplied along with software for all chapters, keep doing successfull record and play back, now u can concentrate on each line execution, try to understand the TSL(Test script language) statements.