AppPresser 2 requires at least a free account with pushwoosh.com to send notifications.
Both Android and iOS require special setup prior to using Pushwoosh, please view setting up push notifications for Android, and setting up push notifications for iOS.
After setting up your Pushwoosh account, login and create a new app.
To configure your app for each platform, go to "Configure" in the left hand menu, and click configure next to iOS or Android.
If it asks you about a Framework, choose PhoneGap Build.
For configuring each platform, you will need to view the instructions at setting up push notifications for Android, and setting up push notifications for iOS.
Once your applications are configured, you can finish the setup of the AppPush plugin.
To send notifications through WordPress, you will need to get your API key from "API Access" in the left hand menu, and paste that into the AppPush settings.
If you are using a free account, be sure to check this setting: