Where can I find the Clock app?
Look through your homepages and in any groups for the Clock app. If you can’t find it then scroll across to the App Library (scroll from right to left) and search Clock in the search bar. Alternatively, you can scroll down (from the middle of your screen to the bottom) and search for Clock in this search bar.
How can I choose a different song as my alarm sound, over the pre-installed sounds?
When you reach the Sound page (step 6), scroll to the top. Here you will find the Tone Store and Pick a song.
Tone Store will take you to iTunes, where you can purchase a specific song. Picking a song will take you to your iTunes library.