You can either manage the proc yourself...
Watching for it, and taking advantage when you notice it.

That might be with an addon like power aura.
Or it could be with a video feed, if you box with IS Boxer.

This is going to be a lot more work on your part, but you should get better returns on that work.



The other alternative is to just build the proc into your regular DPS rotation, and forget about it.
Depending on what you're boxing or how many you're boxing, this could be your best route.
There can be a lot going on.

Checking wowhead, successful Frostbolts, Frostfire Bolts and Frozen Orb hits have a 15% chance to give you the proc.
Blizzard ticks get you a 5% chance per tick.
And the buff lasts for 15 seconds and stacks up to two times.

With the proc, your Ice Lance does +25% damage for 15 seconds.

You could macro a string of Frostbolts and Frostfire Bolts, that takes 7-8 seconds of casting.
And follow that with an Ice Lance.
Play around with that anyway.

Less of a headache, but not as optimal.