You will have to follow below provided steps to become a scientist -

1. First of all, you will have to earn a bachelor's degree.

2. Get a master's degree as most of the research positions require candidates with that. Once you are done with it, go for Ph.D.

After getting all the required qualification, you can try for DRDO, ISRO etc as they conduct their own entrance and if your academics are really good then they have a criteria for direct recruitment as well.

Good Luck!!!