Instructions
Equip the javelins into the character's inventory by pressing the inventory hotkey, normally B or I, and clicking the javelins and dragging them into the weapons slot. Press the B or I button again to close the inventory.
Click on either action icon located next to either the health or mana potion level. Select the Throw option from the list of available actions. The action button next to the health level is defaulted as the action used when clicking the left mouse button. The button next to mana is the action used when clicking the right mouse button.
Use the mouse to aim the direction of the javelin toss, or to aim at a specific target, and click the mouse button that corresponds to the throw action.