OxWall does not send Push notifications.
I understand "Push notifications" that are sent to mobile phones from an APP, but the mobile version of OxWall is a web and not an APP, so OxWall cannot do this.
I bought a plugin that should do this but it never worked and the developer is still here and the nickname is changed from time to time. If they offer you a plugin that does this, ask in the forum if it is reliable.