Dear Student,

first decide what you want to learn online. There are many paid and unpaid courses present in the online platform for every exams. google and youtube is the best as they provide you the best knowledge of the course for free.

Also there are some famous platforms are there you can learn whatever you want like Unacademy, Byju's, Vedantu, Coursera, Udemy, Udacity, edX, etc. Just select your course and start learning.

good luck :)