Start here: Ubuntu on Launchpad. If you are registered you can file bugs on this page and this is also the place where those reports you filed end up with.
Only the 1st bug that is unique will get accepted though and you will get a prompt stating it was already submitted. Have a look at this example (see the image below). It is a bug about X.Org X server and it has a question to include log files at comment number 2 (
apport-collect 921139) and several replies (see #3, #4 and a lot more further down) in there with log files that got collected when the bug was reported.
At the top of the link you will see how many people are also affected (11 in this case) with this bug and what packages are envolved and what the status is of this bug: