The idea of this build is being an Arthas, that your team loves! That means helpful and effective.
This build has pretty high survivability ( you can solo knights an lvl 9), serious control (with Sindragosa and basic howling blast) and serious damage ( with buffed Frostmourne).

First things first, early on you want to kill enemy minions. Just turn on your frozen tempest and do some clean up. If you are with an ally on the same lane, try to freeze an enemy hero and attack him with with frostmourne hungers charge, and then back up ( if there are towers or more enemies ahead). And just cycle that, if you will cooperate, you will get a good kill. If you don't get a kill, just chase your enemy with frozen tempest on (it will slow them and do damage).

Don't forget to collect healing orbs for that Regeneration master buff.

In the midgame you will become semi-independent. If you see that everyone is busy and doesn't really need help, go and solo a knight camp. Use all of your cooldowns (except your ultimate) and you will be fine.

For kiling enemy heroes use the same freeze and hit tactic as you do early game.

In team fights use you sindragosa (try to aim it heroes as well, as heroes). Do casual body-blocking if your ally is being chased, use frozen tempest all the time (it will make things so much easier if enemy heroes will try to escape in a teamfught)

Almost same thing as in mid game, only you will have to try and stay with you team all the time. But getting a camp won't hurt. Tank bosses (if you are sure you are safe, you can even solo one).

An ideal teamfight scenario: You engage in a 5v5 teamfight, use frozen tempest and other cd, don't get yourself killed, but do soak up some damage for your allies, and then, if enemy heroes are backing up a little to regroup, use your sindragosa (with absolute zero at lvl 20) and freeze them in place. That means that their ranged heroes will most likely be closest to your allies (because that is what happens when a team is regrouping) and you will kill their healers and ranged assasins easy. The rest of enemies heroes will be slowed down, so you can chase them and freeze them. Let your teammates do the rest.)

1) Use frostmourne hungers on cooldown
2) Don't use frozen tempest if you are attacking 1 enemy mob/mercenary.

That is basically it)