First, go to App > App Management in Admin Console.

Add from App Store

1. Tap + Create New button
   
   
2. Tap App Store 
   
   
3. Input a keyword and tap Search button
   
   
4. A window pops up with results
   
   
5. Select the App you want to add
   
   
   
6. Check the information which is automatically filled in
   
   
7. Tap Save button to add

Add from VPP

1. Tap VPP button
   
   
2. Tap Sync VPP Apps button
   
   
3. ESP will instantaneously contact Apple's VPP to grab the most updated Apps list, and will have the following message appears:
   VPP Sync is in progress, please wait .....
4. If the App is not yet listed, or if you want to purchase more license for an App, please tap Manage VPP Apps button. You will be diverted to Apple School Manager login page, please login and manage App Purchase in ASM.  

Add Ad Hoc App

*App which is not listed in App Store

1. Tap + Create New button
   
   
2. Tap Ad Hoc App tab
   
   
3. Fill in the field and upload .ipa file ( *Maximum file size is 20MB)
   
   
4. Tap Save button to add