absolute beginner? dont know what do or where to go?

With keeping in mind that you an REALLY AN ABSOULUTE BEGINEER i suggest you to learn calculus first. Physics is fun, no doubt but also incomplete without math. I can safely say that almost 70% of physics is math on an average. Knowing and understanding calculus will make your life simpler and makes your prep smooth. Quick calculus is the book i found quite helpful while self-studying calculus. math is the knife and physics is the apple.. become the newton now. :p

OK, AM DONE WITH CALCULUS, NOW WHAT?
There are many books out there but the golden standard book is HRK(Halliday Resnick Krane) . This is used by many of the aspirants and proved to be very helpful in strengthening your concepts however i personally found the alter version i.e HRW more helpful. [link in books section!]

FOR USA participants-
Mechanics is your first step [F=ma] so a good start would be doing blue Morin [link in resources].
completing HRK/ HRW after that along with some high standard books[again in resources] should be enough for any of the later stages.
FOR INDIAN participants-
a popular golden standard book in india would is HCV-Concepts of physics which can be found in almost any book store. this gives a good strength in the basic NSEP level followed by high standard books[available in resources] should be enough for any of the later stages.

more info will be updated as and when i get more volunteers here. this is all i can provide at the moment with my current knowledge.

the preparation strategy changes from country to country.

Here is a general advice given by a previous IPhO medalist himself. [ its kind of biased towards the american style of olympiad proscess but nevertheless helpful]

Another great place to go to for guidance is the Physics Olympiad discord server or PhODs in short. Its a server for anyone who is interested in physics and wants to take their studies to the next level by looking at more topics and in more depth. they have over 500 problems in store of different levels of difficulties and is a community with amazing people. i myself have learned everything i know about the Olympiads from talking to people from this server. An original of theirs which i find quite interesting myself is the OPhO- online physics Olympiad which is help annually. For more info join the server!

NOTE ON THE RESOURCE SECTION-
this section has few books of the same level. its often the choice of the reader here. you may initially try both the book [ the books of same level are mentioned in resources] and follow the one that sets you.