In order to complete 12th class syllabus and JEE Main in 2 month you can make your proper time-table according to your comfort and your strength and weakness. You can add all the topics from your boards and JEE Main preparation.

It will help you to complete your syllabus on time. You can also set your daily and weekly targets.

Focus on the topics which carries more weightage in the exam.

Work on your basics to make your concepts clear and to build your fundamentals strong. You can take help of NCERT books for that. 

After, completing your NCERT you can recommended other books as well.

Refer previous year papers to understand the exam and to know the level of the questions asked in the exam.

It is advisable to clear all your doubts. You can take help of teachers or you can join study groups. 

In the last days of your preparation you can practice mocktest series as much as you ca to analyse your preparation level. So, that you can imporve your performance.

It is good to learn from your mistakes and not to repeat your mistake.

All the Best!!