Start the truck up and get it to normal operating temp. Turn it back off. Take the valve covers off. Start the engine back up. Listen for the rockers that are tapping. Tighten until they are not tapping anymore. Do not tighten anymore than necessary, just until it stops tapping. Once all the tapping has stopped turn the engine off and reinstall the valve covers. That's it. Make sure you have fire extinguisher or a water hose close by.