There are several ways to file a bug report through Bugzilla.
One of the entries in the Help menu is called Report a Problem. This menu entry should cause a browser window to launch and open Bugzilla to the Gnumeric page.
Alternatively, users can click on this link to access the Gnumeric page in Bugzilla.
If neither of those shortcuts work, the user must use a web browser to access the following location:
http://bugzilla.gnome.org/enter_bug.cgi?product=Gnumeric
The user may be asked to login, by giving their account name and their password, when they begin their browser session with Bugzilla. See Section 17.3.2 ― Logging into the account for an explanation of how to login to Bugzilla.