Hey Jahnee!
The Azerite Essences you’re after to power up your Heart of Azeroth are gated behind the intro questline to Nazjatar. I’d recommend you complete these first through a quest called “The Wolf’s Offensive”, or by returning to Nazjatar/Mezzamere via the portal that you unlocked if you completed this part already. As you progress there you’ll either get a quest to go visit Magni and MOTHER in the Heart Chamber in Silithus, or you may already have a quest there depending on what you’ve done so far.
All of this will require some regular questing, and the Comprehensive Nazjatar Guide on our fansite WoWhead should help you explore this further.
Best of luck!