In "The Cay", how did Phillip help Timothy and what did Timothy want Phillip to do?In chapters 9 through 12.
Timothy helps Phillip in a great many ways. Indeed, without Timothy's help, Phillip would not have survived the attack on the ship, made it to the cay, or managed for himself on the island. In chapters 9-12, Timothy weaves a rope from vines for Phillip to use to guide himself around the island (since he is blind). Timothy also makes a cane for Phillip.
What Timothy wants Phillip to do is to become more independent. He foresees, perhaps, a time when he will not be able to help Phillip, and wants his friend to have the skills necessary to survive on his own. To that end, he insists that Phillip weave palm fibers into sleeping mats for their hut. He also encourages Phillip to climb into the palm tree to get coconuts. Phillip does these things, although at first he is angry at Timothy for pushing him.
In the end, it does become important for Phillip to have the skills and confidence to survive independently. These are some of the greatest gifts that Timothy of Charlotte Amalie bequeaths to his friend.