Now, you could go keep adding criteria, such as the date range of the recordings, or specifically exclude certain artists--but this should be plenty to get started. Under the instructions, let's check the limit box and set the playlist to limit at 100 songs--although you could also limit by a length of time or say memory size. By default, iTunes will choose songs at random, but since this is a playlist of highly-rated songs, let's have it select according to rating.
I'm also going the check the box for "match only checked items" since I don't want the playlist to include songs I've unchecked in my library. The "Live updating" will also get checked, so that newly rated songs will automatically be added or deleted from the playlist.