How are people trained in research and analysis wing?

RAW recruit directly. Staff Selection Commission Organize a exam called Deputy Filed officers Under cabinet secretary,there you can appear.

On other hands,

RAW doesn't recruit directly it pick candidates from Army,police or other forces basically, but it also recruit from general public, eg: universities, corporate houses etc. RAW approach after keeping an eye on the suitable candidate and then offer a job. there is no way you can directly approach RAW, they have no website or info of any type on net, if they like you they will come to you.