Two wires to one lug - Strip both wires back 1 CM. Twist each individual wire. Then twist the two wires together. Apply solder to the two (joined) wires. Apply solder to the lug and bring the joined wires onto the lug and you are done. Been doing this since I was 14 years old.

You can also place some shrink tubing over the new solder job to make it look nice