Use APKPure App
Get OneSignal Sender old version APK for Android
Send notifications to your clients OneSignal form your phone Directly
This app permit OneSignal send push notifications to your clients from your Android phone Directly or tablet.
Simply save the App ID and App Key of your OneSignal OneSignal App from your account and start sending push notifications using With Their REST API.
*** You need an account OneSignal, and get your details APP from App Settings -> Keys & IDs