In netrw, you can delete files and directories by navigating over the
target of deletion and hitting D.
By default, netrw will use rmdir when deleting directories. This means
that if a directory has files in it, then it won't be deleted. rmdir
rightly gives an error when the target directory isn't empty.
Not to worry though, netrw can be configured to use rm -r instead of
rmdir when deleting directories.
:let g:netrw_localrmdir='rm -r'