To insert an instance of an existing sprite onto the current level, you must first select it (in the Builder toolbox) and then simply drag it from the Toolbox onto the level canvas.
While it is selected, you can either delete it by pressing DELETE or duplicate it (make a copy) by pressing ENTER.
Sprites added to canvas can be moved by dragging it with the mouse or with the cursor keys. Multiple sprites can be selected simultaneously by left clicking around then and dragging the selection rectangle around the targets. Alternatively, while one Sprite is selected you can hold down the CTRL key and select additional Sprites.
Additional options can be accessed via the pop-up menu that you call by right-clicking the sprite.
See alsoCreate Sprite