First of all, you need to use the home button to pull up a menu with 'Input' on it. Use your remote to either project or screen mirroring, depending on what casting you want to do. It’s possible that you’ll need to select 'Apps' first. Then, open settings on your desktop and select 'Devices'. Choose 'Add Bluetooth or other device', then pick 'Wireless display or dock'. Finally, just select your Smart TV from the list of devices to start casting.