Use the mouse to click the active buttons of the calculator. The five buttons across the top select the five different options at the bottom of the screen.
If you don?t like clicking buttons, they all have corresponding hot keys:
Arrow keys: Arrow calculator buttons
Enter: Enter calculator button
Space: Stat calculator button (used for viewing stats)
1-9: 1-9 on the calculator (used for quick picking of menus)
Z,X,C,V,B: Hot keys for calculator buttons across the top.