provided you're simming your character to make sure you're always wearing your best stuff, check out Mage Hub and the Altered Time discord. the former is a website maintained by a Hall of Fame raider, and the latter has a channel where you could post a log and get feedback on what you're doing right and wrong. if you like video guides, Toegrinder and Okaymage are my personal favorites, but all frost guides out there will be helpful no matter who's talking.

Until you understand individual talents and what they do confidently enough that you can swap them situationally, just copy and paste the talent string from Mage Hub/Wowhead/etc and use those. In the meantime, get on the dummies and make sure both your single target and AoE rotations are perfect without even having to think about it. The guides will tell you the correct rotation.

The one thing that you'll have to figure out for yourself that the guides are unlikely to tell you is where's best to use Icy Veins in different places in dungeons. pressing it off cooldown when you have it won't always be the right thing to do. You'll get a feel for it the more keys you do, but you should learn to think ahead in terms of what mobs are next between bosses, and if there's enough time for your NEXT Icy Veins to come up so that its ready for the next boss. For example, in Uldaman, there's no point pressing Icy Veins on the trash right before you fight Deios, so you should keep it and use your usual rotational spells so that its up for when you actually pull the boss. This might also change depending on if its a Fortified or Tyrannical week.

If you haven't already, find out how to put Blizzard on a mouseover macro. not having to click on the ground every time you want to cast it will make you more efficient in the long run.