I am playing a witch doctor in beta. I have a bow equipped. How do I use it? Every time I click an enemy I just use my magic attack.
That said, there's not likely to be a lot of value in using said autoattack. Most of the importance of weapons, including bows, is the abilities that they allow you to perform (many demon hunter abilities, for example, require a bow), the weapons damage on them (which is the basis for all spell damage in the game), and their stats. Their actual autoattack is of very rare use.
auto attack is only useful if you have the passives that grant a bonus to your basic attack. like the Wizards Virtuoso or the Demon Hunters Fundamentals