To make the Wish List view useful, you need to add something to the list if you haven't already. Just go to the iTunes Store in iTunes, select a song or album, and choose Add to Wish List from the price drop-down menu.
Your Wish List has been available in the iTunes Store for some time. Just choose the Wish List option from the Quick Links on the store home page. Viewing your Wish List in your own music library, however, is new.
It took a little time, but the promised Wish List is finally appearing in iTunes
To view your Wish List in your own library, click the very nondescript drop-down menu button below the iTunes search field — it looks like a square with three lines stacked on top of each other. From there, you can see the music, movies, and TV shows on your list, and you can make purchases, share your wish selections, and delete them, too.
The Wish List feature is a little more convenient now that you can access it from pretty much anywhere in iTunes, but it sure would've been great if it had actually shown up when Apple first said it was there.