The scores from the Prelims exam is not counted towards the final score however the scores seek to determine the merit. The first and foremost step is , to begin with, the NCERT books and mark important topics. Arrange them properly. Here are some strategic tips:
1 NCERT Books
Start with NCERT books for clarification of the basics and build on the foundation.

2 Newspaper Reading
Stay updated with current affairs through reading newspapers and magazines. This helps one to master the current affairs in areas like developments in economic, political, social issues and policy changes.
Here are a few resources which can be referred for the preparation for the Exam

A)Current Affairs

-The Hindu
-The Tribune, Himachal edition.
-PIB analysis by Jatin Verma.

Magazines
-Yojana Magazine.

Books

Indian Polity by M. Laxmikanth.
India Economy by Ramesh Singh.
NCERT books Class 9–12th standard.

B)History

NCERT books 6–12th
History of Modern India by Bipin Chandra
India after Gandhi by Ramachandra Guha

C)Geography

Physical and Human Geography by G.C. Leong.
Oxford Atlas
Science and Technology
NCERT books from class 6–10th standard.

D)Environment and Ecology

Shankar IAS notes

E)Himachal General Knowledge section

The wonderland Himachal by Jag Mohan Balokhra
Himachal Pradesh, History, Culture, and Economy by Mian Goverdhan Singh