Distant attack is a kind of ability. Equip certain weapon to the weapon slot to enable the ability. Various patterns of "Bow" and "Arrow" combination are available. 

There are jobs which cannot equip the distant attack weapons.

Go to your "Action command window", choose "Ability" while targeting an enemy. From the ability list, choose "Distant Attack".

After you have confirm the target, you will shoot the arrow towards the target you have chosen.