Feed the 4043 aluminum wire to the welding torch. Insert wire through the guide tube and over the roller. Align it with the hole at the end of the wire liner, and push it manually into the hole for a few inches.
Tighten the wire, with a tensioner.
Adjust the wire speed and power settings of the torch, following the manufacturer's instructions. As wire diameter increases, voltage requirements increase, as does, in general, required wire speed. Voltage requirements also vary between different kinds of welding (ie, MIG vs. TIG).
Fire the torch. Move it in a zig-zag motion over the surface of the metal to which you are welding. If you are welding thick metals or wires, consider using a zig-zag motion in a relatively straight line; if you are welding thin metals or wires, use a curved zig-zag motion. Consult your manufacturer's instructions for details on the specific motion.