Description (From Recipaedia)
A crossbow can be used to fire various types of bolts.
The crossbow uses 3 types of bolts:
Using The Crossbow
Bolts can be lost because they bounce, so be sure to watch carefully. They can also ricochet back from your target, killing you. Don't shoot it from 15 or fewer blocks away.
Loading a crossbow
Loading a crossbow is more complicated than a normal bow. Watch the video below.
When the Crossbow is selected in your hotbar, the sneak button is replaced with an edit button (paper and pencil). Tap it and the window shown below will come up.
You then draw the string back by sliding your finger.
Then you move a bolt from inventory onto the Crossbow.
It is now ready to fire.
Note: On a computer, press "G" instead of the paper and pencil.