want to give 10th and 12th boards again

I had a pathetic cgpa in 10th and 12th grade. barely passed. I was an isce board student. I want to give state board exam and get a good cgpa. State board, i want to do for both 10th and 12th. What is the procedure I must follow? I am currently pursuing my ug,but am willing to prepare side by side for the boards. Kindly help.