Using asteroids.
In Pale Blue Dot, Sagan talked about people living inside the bodies of the Oort cloud. They would live in one until they used up its resources, then move to the next. It’s possible our Oort cloud mingles with Alpha Centauri’s Oort cloud. Sagan envisioned the people making their way into Alpha Centauri’s Oort cloud. Eventually, the curiosity about the planets in that system draws them closer to the star.