How do I use elephants properly?

[Viking]

...2) retreating from missile fire, especially fire arrows; and 3) using them in tandem with another unit right at the elephants' feet (skirmishers or cheap melee infantry are great for keeping enemy skirmishers out of range).
...
R:TR takes a more realistic (though less enjoyable) approach: the elephants are much easier to kill, especially with javelins, and they rout if you breathe on them wrong.

Also in vanilla those javelins are very deadly for elephants, so for gods sake keep `em away from those!