Am I eligible to apply for the LLB admission after Post graduation course with 45% marks?

Yes, you are eligible for the LLB admission after Post graduation course with 45% marks, the eligiblity criteria for the LLB admission is that the applicant should have completed B.A. or B.Com. or B.Sc. degree with minimum 40% marks (35% for SC / ST). for admission you need to appear in the one of following entrance examinations:

AIBE: All India Bar Exam
AIL Entrance Test: Army Institute of Law B.A. LL.B Entrance Test
AILET: All India Law Entrance Test
AMU LLM Entrance Exam: Faculty of Law, Aligarh Muslim University, Post Graduate Law Entrance Exam
AMU Law Entrance Exam: Faculty of Law, Aligarh Muslim University, Law Entrance Exam
BHU UET Law: BHU LL.B. Entrance Exam
BVP CET Law: Bharati Vidyapeeth University Common Entrance Test
Christ University Law : Christ University Law Entrance Exam
CLAT: Common Law Admission Test
CUSAT CAT Arts and Humanities: Cochin University Of Science And Technology Common Admission Test
CUSAT LLB Entrance Exam: Cochin University of Science and Technology BA/B.Com LL.B Entrance Exam
DU LLB Entrance Exam: Faculty of Law, Delhi University Law Entrance Exam
DU LLM Entrance Exam: Faculty of Law, Delhi University Post Graduate Law Entrance Exam
GLAT: Gitam Law Admission Test
ILI CAT: Indian Law Institute Common Admission Test
IPU CET Law: Guru Gobind Singh Inderprastha University Common Entrance Test Law
JMI Law Entrance Exam: Faculty of Law, Jamia Millia Islamia Law Entrance Exam
JUET: Jammu University Entrance Test
KLEE: Kerala Law Exam
KLSAT: KIIT Law School Admission Test
LAWCET: Law Common Entrance Test
LSAT-INDIA: Law School Admission Test India
Panjab University B.A. LL.B: Panjab University B.A./ B.Com. LL.B Entrance Examination
Panjab University LLB : Panjab University LL.B Entrance Exam
PGLCET: Post Graduate Law Common Entrance Test
RULET: Rajasthan University Law Entrance Test
Sastra University BA LLB Exam: Sastra University BA/B.Com/BBA LLB Entrance Exam
SET Law: Symbiosis Law Entrance Test
ULSAT: UPES Law Studies Aptitude Test