Aslam-o-Alikum Dear fellows,
Due to uncertainty of lock-down, I bought books in bulk the very first chance I got so that I might not face any trouble in future.
For Political Science I have collected following books:
1.Sages of the ages
2.Constitutional and Political History of Pakistan
3.Political Science theory and Practice
Unfortunately I couldn't lay my hands on Muslim Political thoughts and World Constitutions.

Could any senior guide me, how should I prepare the subject from aforementioned books; which topics should I cover and how to make notes of such a lengthy subject?

The above books are, for now, sufficient, but after you are done with topics covering by these books you can go for "Muslim Political thoughts and World Constitutions."
But, to be really honest, i did not find "Muslim Political thoughts book by M.Aslam Ch.," up to the mark. If you find its replacement, do tell me.

Lets answer your query:
1. Political Science theory and Practice is sufficient for, part-2 of paper-1, topics like, liberty, state, forms/ systems of governments etc... It also highlights few Muslim thinkers so it will offset absence of "Muslim Political thoughts book" to certain extent.
2. Constitutional... history by Hamid khan is good to cover Pakistan post partition area, judicial, constitutional and political history and issues. (That means Part-2 of paper-2 specifically its Pakistan related aspects).
Plus, it also includes comparative analysis of all 3 constitutions, 1958,'62 and '73.
3. Sages of Ages ( i have not read it, but a friend who did, said, it covers "western political thinkers' part." for my (western thinkers') preparation i preferred book by Judd Harmon's book.) For this book other members may guide you.
4. World constitutions book covers political systems and Constitutional comparison part (paper2). (since you don't have it, right now, use above books for remaining syllabus)
Hope it helps!

Thanks for your comment @The dream of rain
I was checking Mazhar ul Haq's book and found that most of the topics need to be covered, apart from certain topics at the start. Am I right?
And about Hamid Khan's book, would I need to cover it whole?

And how should I study them and make notes, I don't have much familiarity with this subject.

As soon as lock-down eases I will try to grab World Constitution and book on Muslim Philosophers. I hope these will be sufficient then!

One more thing, I have opted Constitutional Law also. Would I need any other book along with World Constitution for this subject to score good marks?

Yep! most of topics in Mazhar ul Haq's book need to be done, but that does not mean ALL. Do only which are important and frequent.

You don't need to read entire Hamid khan's book, just read certain topic you feel to do. Secondly, If you have covered Pak. Affairs Post partition well, then you just need to use Hamid khan for some topics, because post-partition portion is co-related to it.

For notes, do as you do for other subjects. The purpose of notes is to ease your revision and keep main points and data at hand. However you feel easy follow that.

I don't have Constitutional Law as optional, so other member may help you in this regard!

Hope it helps!

Thanks alot mate