You can’t start this mission until after 8pm, so you can either play some mini-games, buy the saloon in town and save there (if you have the cash), or set up a campfire outside of town to save and then fast-forward the time to after 8.
Once the mission is available; head to the docs again to meet up with Nigel. Drive him to Ridgewood Farm (you may already have been here on the Marshal’s mission) and you need to shoot the skull sitting on the porch in the distance.
Make sure your aim is bang on before firing and then you’ll be challenged to shoot a hat out of the sky. When it’s thrown up, turn on Dead Eye and then aim your gun over it to target it automatically. Press fire to shoot it out of the sky.
Clearly this isn’t impressive enough so your challenger confronts you to a fist fight! Use LT/L2 to block and RT/R2 to punch, and when you get him on the ground, press Y/Triangle to get on him and start hitting punch as fast as possible!
Repeat this until his gets back up and pulls a gun on you! Now, you’re not allowed to kill him , so the trick is to use Dead Eye on his gun, allowing you to disarm him safely. Doing this will complete the mission and open up the next character in the storyline, Seth.