Generous people are the ones who give more than is expected of them. It's generous of your friend to take the couch and let you sleep in the bed when you stay over at her place. She didn't have to do that.
When you decide to go one step beyond what's expected of you, you're being generous. A generous helping of food is a bigger than expected scoop of mashed potatoes. A generous teacher is one who volunteers to stay after school to help you with your homework. Be generous yourself: don't forget the letter o when you spell the word generous. Just think of it as a generous act, throwing that extra letter in there.