Reporting a bug to a Debian package is just a matter of sending a specially
formatted mail to <submit@bugs.debian.org>.
The mail should include in the mail body, at the top, a few special pseudo-fields:
Package: <package name> Version: <version of the package> Severity: <bug severity> Tags: <bug tags>
As a consequence, the following is a typical manual bug report (Klingon translation for the shadow package sent by the translator named John Doe):
From: John Doe <john.doe@johndoe.com>
To: <submit@bugs.debian.org>
Subject: [INTL:tlh] Klingon debconf templates translation
Package: shadow
Version: N/A
Severity: wishlist
Tags: l10n patch
Please find attached the Klingon translation of the shadow package.
(encoded tlh.po file follows)