The joints panel has a list of the joint names. Double click on the one you want to rotate to select it, you can tell it is selected when the name is on the text box.
Then you go to the main panel (leftmost tab) and press in the button that says rotate.
Now you can press the big ANIM button and start moving stuff.
Now, in your four views you can control the rotation by mouse (click-drag) in the three ordinary orthogonal (flat, not 3D) projections. Usually this is left, front and top. You can move any two of the three directions in a single move, but which two depends on which window. By example, in the front view you can rotate a leg on the Y axis (like an ankle twist) or the Z axis, like a side kick, but you cannot make the leg move forward like a kick (X axis), you have to use the left or right views for that.
You can lock the rotate function for any axis. Those are the little X Y Z buttons that appear when you select rotate. For starter purposes, deselect two of the three and try clicking and dragging on a window to see if you get the movement you want. If not, use undo, try a different button or a different window until you get used to how the movements operate.
It's not really hard to do, but the sequence of steps needed (bone selection by double-click, rotate button pressed, ANIM pressed, click-drag in view) is not intuitive.
<* Wes *>
If you like to say what you think, be sure you know which to do first.