Deliver Keryn Sylvius's package to Master Mathias Shaw at the Stormwind Barracks.
The badge? Oh, it's nothing, fish - nothing you could handle anyhow. By the looks of you, I'd say Mathias is likely to mistake you for the cheese delivery $g boy:girl; instead of a proper rogue. Regardless, I've been assigned a job and I've made a promise to deliver on that job.
Speaking of which, deliver this package to Mathias and he may give you a small task or two.