Enter in whether to use the bar or clock timer. For bar timer: Enter in the time and length of the timer. When asked "Centered?", type in yes or y to have it in the middle, else click an area for the timer to appear. For clock timer: Enter in the time and radius of the timer. When asked "Centered?", type in yes or y to have it in the middle, else click an area for the timer to appear.
You can use the timer block and edit the colour of the timer.