While holding two weapons a character attacks with both of them in the same attack action, and then can use a bonus action to attack with the off-hand again. A Rogue Thief can attack with the off-hand twice, granting them 4 attack in total at level 3.
I'm pretty sure that's not how dual wielding works. The offhand is NOT used automatically.
Its not used automatically. I attack twice with both weapons as an action and then I have the ability to use both my bonus action to attack two additional times. Look at the animation when you attack while wielding to weapons and see the damage numbers. It's always two numbers and the animation is of the character attacking with both hands.