As you are unaware about the process of JEE MAINS and Advanced so its logical to assume that you don't have any preparation for the examination till now. So its better for you to take a drop if you want to clear JEE MAINS and Advanced in order to take admission in IIT.

In this one year you have to prepare yourself. The syllabus of the exam is of 11 & 12. So if you have good basic understanding, concept clarity and problem solving skills then you will need revision and practicing numerical problems.

Now if you don't have good basic then start reading the topics and clearing the concepts. As you will clear the concepts slowly you will gain the confidence to solve numerical. You definitely have to work hard in order to crack the examination as it is one of the hardest examination in India and the competition is very hard.

For JEE MAINS you may visit the link below:

https://engineering.careers360.com/articles/how-prepare-for-jee-main

For JEE Advanced visit the link below:

https://engineering.careers360.com/articles/jee-advanced-2021

For JEE MAINS 2021 rank booster course visit the link below:

https://learn.careers360.com/jee-main-rank-booster/?icn=jee-rank-booster&ici=jee-text-mapping

I hope my answer helps. All the very best for your future endeavors!