If your present tape is wrapped well, you can use it as a reference. For practice, as suggested above, you can slowly unwrap one side of your present tape and re-wrap it. Pay attention to how the tape wraps around the lever bracket. When you're ready, wrap the new tape on one side of the bar with the old tape still in place on the other side as reference. When that's wrapped to satisfaction, you'll be ready for the other side. You want enough tension on the tape to prevent it from slipping in use, but too much could tear or stretch out some tapes. Pay attention to the amount of overlap, especially if your handlebar has lots of real estate to cover or if the tape mfr wasn't overly generous.

It's not that hard to do a reasonable wrap, and I'm sure you've successfully tackled much more difficult tasks. Just don't be surprised if you spend at least twice the amount of time you think it should require the first time around.