Installing Ruby on Rails

I am completely new to all of this. I was told by a potential employer
if I learned Ruby on Rails and PostgreSQL I would have a job in 6-9
months. My dilemma is that I cant even seem to install it properly
lol. Please can someone give me the prompts and whether I have to be
SU or use sudo. thank you so very much.

I'll add to the list as well.

I agree RoR is hot, but if you are a good developer, you can get a job
in 1 month even without learning RoR...

Cheers, Sazima

I am using CentOS and if possible it would be appreciated to have
links to PostgreSQL as well, thanks. thank you for all of your input.