Choose the sample you like to plot (e.g. Climbing sine)

You'll see the equations of the sample

Open the Options menu (On most devices this can be done by the left selection key)

Choose Plot, if you want to view the Graph

You'll see the sample right now

You can zoom in (5) out (0), move (arrows), evaluate the function (left selection key -> "Evaluate function") or show the function table (left selection key -> "Show Table")

Insert the integral you want to calculate in the form I(x1, x2, f): this will calculate the definite integral between x1 and x2 of function f (e.g. I(2,4,x) will calculate the area under the graph f(x)=x for x between 2 and 4.
or more formaly, this will calculate: