To divide x by y, for instance, enter y, click "/", enter x, then click "=".
A few of the button labels might be unfamiliar. "nCk" is the number of combinations of n things taken k at a time. To compute it, enter n, click "nCk", enter k, then click "=". Similarly, "nPk" is the number of permutations of k of n things. "U[0,1]" returns a pseudorandom number between zero and one.