How did Viola came to work for Orsino?

The Captain, who is from Illyria, tells Viola of Count Orsino, and of his love for Lady Olivia; the Captain also mentions Olivia's recent loss of both her father and her brother, and Viola, having lost her brother as well, commiserates with Olivia's situation. Viola proposes that she serve Orsino, since he is a good and just man; she conspires with the Captain that she may be presented to Orsino as a eunuch, and that her true identity as a foreign woman be concealed. The Captain agrees to help her, and he leads her to Orsino.