AppPresser 2 requires at least a free account with pushwoosh.com to send notifications.
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.
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: