Use the "sprocket" icon in the top right corner to adjust the parameters of the exercises. 
​Treble Clef only? Bass Clef only? Both? With or without key signatures?

You can reset your score and start over with the "three dots".
You can always just practice to get better at various music skills, but if this activity is an assignment, make sure you take a "screen shot" of your final score after practicing and put that either in my Teacher Dropbox or upload it in Schoology - depending on the assignment.
What do you want to practice today?