It might be a sphere a mile in diameter spinning to create gravity. The inside of the sphere would be covered with dirt, gardens, farms and living spaces. Lit from a central LED array to simulate sunshine. The people would be living there for generations. Herds of cows, chickens, sheep and pigs would be needed to be raised for food. Vast hemp fields could be planted to convert carbon dioxide in the atmosphere to oxygen.
At one end of the sphere looking outside would be the command center with landing pods. At the other end would be thrusters. Since the distance would be a minimum of 4 light years, the spaceship would take at least 8 years to get there if it traveled at half the speed of light. That's really fast. Perhaps an unreasonably fast speed. 40 years travel time if we went 1/10 of the speed of light. Still, that's really fast.