As you want to get the details of process to join Indian Army infantry after graduation so here is the information of the same for you:

According to me you must give the exam of CDS which is conducted by UPSC

Eligibility:
Age for Navy 19 -22
Age for Air Force 19 -23
Graduation with 60 % marks from recognized university and its equivalent.
Un married
Citizen of India

Syllabus
General Science
Math
English
Reasoning

Exam Procedure
Written test
Interview

Goods books for CDS
R S Agarwal quantitative aptitude,
For Gk. Upkar Publication,
Competition success Review magazine.
NCERT Books of class X,XI and XII