Which version of The Necronomicon are you going to be using? Several people have published versions of a "translation" for fun over the years. It's funny you mention this now as I'm currently reading a version by Donald Tyson (Necronomicon, The Wanderings of Alhazred) who is apparently an occult non-fiction writer who took up this project for fun. His version however does contradict itself at times (but then again I'm be surprised if it didn't) and other similar projects and various stories over the years. For example I think he has some aspects of The Elder Things and The Great Race Of Yith mixed up, he mentions both at various times (of course).
One important thing to sort of understand about Cthulhu which most people get wrong is that he's not a god, he's at best a demi-power, though us poor misguided humans treat him as once. Part of the "horror" is that as powerful as Cthulhu is, the real threat he represents is that if awoken the first thing he'll do is throw open the gates to allow his masters who are the real "Great Old Ones" to return. The basic idea is that the various true "Elder Gods" had the stars literally conspire against them, and they moved into a position where they released radiation that was destructive to them and forced them to retreat from this world of face their end. Cthulhu himself is vulnerable to this, but remained behind with the intention of opening the gates then the stars were forced to resume their original patterns over millions of years and it would be safe for his masters to return. Unfortunatly for Cthulhu when he came to earth as a conquerer the races here objected, then depending on who is writing, he was basically defeated by either The Great Race Of Yith OR The Elder Things, traditionally The Elder Things get credit for it which is why "The Elder Sign" is such a powerful ward, though the Yithians do get credit for having done the same thing from time to time before being forced to return their minds back to their own time when the flying polyps arrived. At any rate when Ry'leth was sunk Cthilhu was forced into a state called fgthan (I can't remember the spelling or pronounciation despite having just read it) which has no moral equivalent but it's a state of unlife that can also coorespond loosely to sleep, meditation, or deep dreaming. In this way Cthulhu was safe from his enemies but through his dreams could contact and seduce mortals with his mind, ultimately leading them to find a way to restore Ry'leth from the sea, and then when the stars are right allow him to open the gates to call his own masters back to our plane.
More confusing is when you get into "what the heck are humans" in the most recent version of the mythology I'm reading Humans were a servitor race created and abandoned by The Elder Things for lulz when they were on our planet (they since returned to their own), in other versions such as the expansions done by Robert E. Howard in "The Mound" humans were a slave race of Cthulhu, brought from his original home world, and this is one of the reasons why he is able to contact humans in his current state and guide things, though being trapped at the floor of the ocean his ability to make contact is greatly limited. The name "Tulu" is largely from "The Mound" if I recall. In that story it's mentioned that humans at one point had access to both very advanced technology, including necromantic devices. Humans also possessed the ability to make themselves and other intangible, and limited psychic powers allowing telepathic communication and mind invasion through eye to eye contact, the humans under The Mound retained some degree of these powers although they were a mere shadow of what they once were, and while that isn't Lovecraft (though Howard apparently cooresponded with him) it did make a certain amount of sense in explaining the relationship between humans and the mythos, basically humans were at one time far more powerful and useful creatures but without Cthulhu's patronage we ourselves have degenerated, losing access to our granted powers, and with our current innovations being a mere shadow of the technology we once had as favored servants.
Ah well, I'm rambling. It will be interesting to see what version shows up here. You also have the Chaosium stuff which drew on a lot of increasingly divergent stuff, while creating it's own, as well, and arguably presents the best developed and internally consistent version if you look, but also arguably has among the least amount of input from the original creator in the end.