You'll need to find and commandeer a gunboat to proceed. This usually involves infiltrating a small Omega Force dock or outpost. Expect moderate resistance from guards patrolling the area. Use stealth to clear the dock area, or go in guns blazing if you prefer. Once you've eliminated the immediate threat, locate the gunboat. It will be marked on your HUD. Approach it and interact (E) to take control.
Gunboats are equipped with mounted turrets, providing significant firepower. Familiarize yourself with the controls for driving and operating the turret. You can often switch between driving and gunning, or have an AI companion operate the turret if available. Before setting off, ensure the area is clear and you have a clear path to your next objective. Sometimes, you might need to destroy a gate or barrier to exit the dock area.