Hello my name is Blinks and this is how you play Crystal Maiden. Crystal Maiden is an Intelligence based support. Her Q is a ranged aoe damaging slow, her W disables a single target and does damage to it over time, her E passively gives her whole team mana-regen, and his Ultimate is a devastating channeled aoe attack. Crystal maiden is a great support for players new to dota. Her disabling W & Slowing Q make her great in ganks and lane-harrass early game, and her Ultimate can be a real game-changer in mid and late-game team-fights.
If you are ganking with someone who also has a disable/stun, make sure not to use your W at the same time as they use their disable, as they will needlessly overlap, and possibly cost you a kill. Remember that you are a support and if you are taking kills from your carry you are actually hurting your team. Try not to steal kills, slow enemies so your carry can get them, and ward-damnit! Warding is the most-important aspect of a support and should not be ignored! For an aggressive playstyle, prioritize R > W > Q > E. If your team needs mana you can always put some points into E early. As for items, you want to buy wards, tranquil boots, and a mekanism. If you get farmed, Aghanim's center will let you dominate team-fights.