You can connect your Dell Precision 5550 laptop to an external monitor by using one of the Thunderbolt 3 ports or the USB-C port on your laptop. You will need a cable or an adapter that supports DisplayPort or HDMI output. You can also use a docking station or a hub that has multiple ports for connecting your devices and peripherals. You can adjust the display settings of your laptop by using Windows Settings or NVIDIA Control Panel.