To see what this looks like on the student side check out this article.
1. When your students requests to download an app and Ask to Buy is turned on, you will get a notification letting you know which of your students is requesting an app and what app they are requesting.
2. If you missed tapping on the notification you can always locate it again on your notifications window. Swipe down from the top and tap on the notifications tab. Tap on the Request.
3. A new window will open that will show you all the details of the app from the app store. Tap Approve (or decline).
4. Enter your password (i.e. the password on the parent's Apple ID) and tap approve.