Hello aspirant,

You can become a JRF by qualifying the CSIR/UGC JRF exam after which you can join any University or Research Lab in India as a JRF. After 2 years of your JRFship You will be promoted as a SRF.
When you join a lab as a JRF you can register yourself for Ph.D program in any recognised University.
Research Asssistant/Project Assistant are posts in a funded project which are running in any University or Research Lab.

Hope it helps!!