Is it possible to write and edit etc/default/unicorn using FTP ? RoR, Ubuntu 12.10 server

Hi,

I am trying to follow this guide : https://digitalocean.com/community/articles/how-to-1-click-install-ruby-on-rails-on-ubuntu-12-10-with-digitalocean

I am at this part Now modify your PATH in /etc/default/unicorn: PATH=/usr/local/rvm/rubies/ruby-2.0.0-p195/bin:/home/unicorn/.rvm/bin:/usr/local/sbin:/usr/bin:/bin:/sbin:$

Since I changed to ruby-2.0.0-p247, I would like to modify this in the unicorn folder, however I do not know how. Everytime I try to modify it using filezilla it fails the transfer :

Erreur : /etc/default/unicorn: open for write: permission denied Erreur : Echec du transfert du fichier

and typing "PATH=/usr/local/rvm/rubies/ruby-2.0.0-p195/bin:/home/unicorn/.rvm/bin:/usr/local/sbin:/usr/bin:/bin:/sbin:$ "

as root in the terminal does not seem to do anything because the file remains the same. So how do I do this ?

Thanks