Play through the Tutorial Campaign, it will get you started. In general, the easy thing to do is click on a guy so he's selected, then left click on the ground somewhere to make him move, or left click on another unit to make him attack that unit. It's only when you get into the more sophisticated commands that you'll need to study the manual and practice. Fortunately the basic commands (move, attack, do this, build that) are very simple. Basic Controls Warcraft III: Frozen Throne is played with both the mouse and keyboard in tandem, and the controls can be quite complex and take some getting used to.
