There are two meanings of “will”
The first is that God has free will. He has the quality of doing what he wills. This is part of his essence. It does not separate from His essence. He always had free will, even before He created anything.
The second is that he acts upon that free will and he uses his power to do something. This will is not part of His essence. It’s an attribute of action, not essence. That’s because sometimes God does something (like create) and sometimes He doesn’t. This second will is extracted from the use of his power. Whenever he uses his power to do something, we call this will.