What kind of diffuser did you get? I have a couple of different types: one has "fingers." I rarely use mine, preferring instead to air dry. But when I do, I hold it in place for about 30 seconds at a time before moving on to another section of hair. With the fingers I sometimes place the cup close to my scalp, with the fingers touching. You can also cup the hair in your hands, pushing toward your scalp to scrunch and encourage curls. I also bend my head over to get the hair underneath. The point is to dry your hair without disturbing your curl formation.
I don't recommend using it every day--it's still heat and can dry your hair out. Hope that helps.