Hey student, as you have mentioned you got 68% in your boards, I assume you are worried regarding the 75 percent minimum in boards eligibility criteria for the exam. However you need not worry regarding that as according to the notification release vide March 2 by NTA, the 75 percent minimum is no longer a criteria to be eligible to appear for JEE Mains 2022.

Regarding preparation, I would advice you to keep aside your marks in boards and completely shift your focus towards your attempt at JEE. Begin with the most demanding topics in the exam by going through the previous year papers, link for the same has been provided:

https://engineering.careers360.com/download/jee-main-sample-papers-previous-years

Remember you need not study everything to secure a decent percentile in the exam. Rather did you know that se curing 50% of total marks get you to 99+th percentile , that's a fact! so work accordingly. The second session for JEE Mains 2022 starts on 25th July, so you have limited time, give your best.

Hope that helps, all the best!