For Quantitative aptitude, start preparation with NCERT/CBSE books of 8th standard to 12th standard. Solve Profit and Loss, Time distance speed, Ratios, Probability to Permutations and combinations questions. Give some time to yourself to catch the previous things. Through this, you will have an idea about the contents of quantitative aptitude. Try to solve many question or you can teach somebody that helps you to clear you concept more deeply.