The old ones have called me need material to research
Start with the lovecraftian short stories.
Synchronicities! there’s some great audio books on you tube.
I love this narrators voice
U try carl nagel its easy. Or donald tyson i tnk
I second the above advice to read the fiction of H.P. Lovecraft if you haven’t already, and to build on that, I recommend Necronomicon Gnosis by Asenath Mason and the Black Book of Azathoth by S. Ben Qayin.
Donald Tyson’s stuff is okay, but he attempts to shoehorn the Old Ones into a Kabbalistic and elemental framework on the Tree of Life, whether they fit or not, which, in my opinion, is not very accurate. I do however, highly recommend his Necronomicon Tarot deck. The art is phenomenal.
Read the stories first as it will give you an idea of what kind of energies and power you’re working with. Not just Lovecraft’s but also the peers who extended the mythology.