I like aptitude , first you need a Root Terminal, from the knoppix penguin in 5.3

Code:
aptitude update
-- wait for it to complete, (need internet connection)
Code:
aptitude install csh
-- you can do
Code:
aptitude search csh
to see if update found csh , (see info aptitude and aptitude --help)

You should be good to go. You will a hdd install or a persistent image or it will NOT keep.

Good luck . Your mileage may vary.

John