It is great that you are thinking of pursuing IPM being in class 11. You have enough time. You can think of starting with Pearson’s IPM entrance guide. Figure out if you can solve the questions or not. If required, join online coaching classes like CareerAnna.
Finally, be consistent in your work and start building your resume right away. Back your hobby with certificates, participate in competitions, and any other significant achievements you may have made along the way. Volunteer at a local NGO since social work is highly appreciated on your CV.