如何在Angularfire中的数组上设置键名

I am creating arrays using Angularfire but I am unable to set the key name. Firebase is automatically giving me a cryptic key (eg Jm9vLy8Lye-KS35KsmL) but I would like to set it myself to something more meaningful. It is unclear how I do this in Angularfire. I am using the $add method on $firebaseArray:I am creating arrays using Angularfire but I am