Your study plan depends on your experience, familiarity with the content, and the timing of your test. Have you scheduled your test yet? How much professional experience do you have with the core CISSP domains?
I would suggest starting with CISSP CBK, and the first objective is to study NOT for the purpose of passing the exam, but rather to grasp and to understand the materials. There are plenty free learning materials online to choose from.
Once you have gone thru the entire CBK, and have a firm understanding of what CISSP is about, then go back to detailed study for the exam.
Also before anyone pounces on you for mis-use of the designation, if you pass the CISSP exam but don't have the correct experience you will be an Associate of (ISC)2 and not a CISSP-Associate.
Please take a look at this subreddit r/cissp thread:
Or this one (for guidance):