This is quite a simple question:
I just need to open a file (this filename is galfit.feedme). I can view the file with view galfit.feedme when I\'m in the directory
For editing use
vi galfit.feedme //if user has file editing permissions
or
sudo vi galfit.feedme //if user doesn't have file editing permissions
For inserting
Press i //Do required editing
For exiting
Press Esc :wq //for exiting and saving :q! //for exiting without saving