Question

how can i delete an entire file using vim?
as in what is the command to use?

Answer 1

Why not use the 'rm' command outside or in a shell of vim?

Answer 2

Do you want to delete it from disc completely or just empty it?
In the former case you jdunn32's answer is correct, take the shell and use 'rm' or just call it from inside vim:

:exe "!rm" expand("%")

To empty it, I would go to the first row with 'gg' and the remove all content with 'dG'.