This site is screwing up for me so the talent and ability paths are wierd, just bear with me.
First , Choose either the safelane or offlane to support. Get a level of sacrifice first to deny a creep right off the bat. Keep harrassing the enemy with frost blast, but make sure you have spare mana as sacrifice in the early levels have quite the cooldown time. Keep sacrifing whenever the cooldown is off adn try to sacrifice full health melee creeps for the maximum mana gain. During teamfights, spam your abilities and make sure everyone has ice armour on. Try to hold on to your ultie until the enemy are nicely packed together for max effieciency. Mek whenever healthbars go low and force staff when enemy is on top of you/your teamates. Just try to stay alive and get off as many abilities as possible.
Hope this guide helps, peace.