if you want to open a file with vim from the console, you can
if the file does not exist, vim will open it anyways, and create when you do the first :w
if you want to open a file not in the `pwd` you're in bash, you have to type the full path
inside vim, :e is the command to open files, and it will start from the directory you opened vim. If you opened it from the console, probably it'll be your $HOME dir.
type :pwd to find out where vim will first look at.
inside vim, you can type absolute paths, like :e /tmp/file.c
Depending on your vim options (@compile time), you should be able to 'edit' a directory. Then it'll list you all files there, and you can edit whatever is there.
more info in :help edit-a-file
:help has tons of info. the first 'user manual' sections are really useful as well as first reference manual sections.