A wire or wire bundle is represented by a multi-segment line. To draw a wire, position the cursor in an open area of the circuit, click the right mouse button, and select "wires" from the menu. You will see a small circle appear at the cursor. This is the beginning end of a wire. Move the circle to the place where you want to start the wire and click the left mouse button. Notice as you are moving the wire end around that red messages will appear in the blue message bar from time to time telling you why the wire cannot be placed at a given spot (e.g., it is right on top of some element). As long as no message is showing the wire end can be placed at the current spot. If there is a message, then clicking the left mouse button will have no effect.
The wire end can be placed in any open area, or it can be immediately connected to an input or output of an element, or another wire. When the wire end overlaps an unconnected input or output of an element (represented by a white circle), or another wire, the wire end will become green, indicating that the wire end can be connected at that place. A new wire end will be connected when you left click only if it is green. If it is not green then the wire end will be placed but not connected (later you can drag it somewhere and connect it, or connect something to it).
Once the wire end is placed, move the mouse to draw a wire segment and the next wire end. Left click to place the new end. If placing it also connects it, then you are done drawing the wire. Otherwise move the mouse to draw the next wire segment and the next wire end. Repeat until you connect the final end. Right click to stop drawing the wire before connecting it to anything. Right clicking always terminates the drawing of a wire.