I am not too sure if "foreshadow" is the correct word to use here. Let us remember that foreshadowing is when the author plants hints or clues about what is going to happen later on in the novel. A good example would be the numerous times that Okonkwo expresses his rage and anger, which clearly foreshadows the murder that he commits later on. However, Chapter One doesn't really foreshadow the arrival of Ikemefuna into Okonkwo's family, it just tells us that this is going to happen. Consider what it says at the end of the chapter:
And that was how he came to look after the doomed lad who was sacrificed to the village of Umuofia by their neighbours to avoid war and bloodshed. The ill-fated lad was called Ikemefuna.
Thus we can see that there are no hints or subtle suggestions that this is going to happen. The text rather states it openly. Therefore I would argue that "foreshadow" is not the correct word for this question. Having stated a brief history of Okonkwo, which explains how he managed to be successful in spite of the shortcomings of his father and his upbringing, the narrator concludes the chapter by explaining how Okonkwo's position in the tribe led him to be responsible for Ikemefuna.