How do obtain Holy Word: Salvation for a Holy Priest?

In Development The War Within Patch 11.0.5 PTR
1

I am a level 78 Holy Priest and I was researching that you get Holy Word: Salvation at level 50. I can’t find any quest to learn the spell and it is not on my Spellbook. How do I learn Holy Word: Salvation?

2

its a talent. Its shared between Apotheosis in the class tree!