you have to go to the fire planet. get past a few things and then talk to the red knight.
You get it from the ice knight on the ice planet.
When you beat a planet (jungle, fire, ice), the space knight there goes with you. Sir Peleas is outside the door to the lair of the Fire Beast (robot dragon) and gives you the Ice Arrow to use against it.
At the top of the ice mountain.
Sir Peleas is deep within the volcano, at the lair of the Fearsome Fire Beast (a robotic dragon). He will give you the Ice Arrow to defeat it. (see related question)
the guy at the door fives it 2 you
in poptropica you need to talk to the fire knight and he will give you it
If you pay the fee on astro knight island then play it.
Sir peleas gives it to you at the bottom of the volcano cave. (see related question)
To shoot the ice arrow on Astro Knights Island in Poptropica, you need to equip the bow and arrow from the armory in the castle. Aim the bow at the ice shard above the dragon's mouth and release the arrow by clicking or tapping on the screen. This will break the ice shard, allowing you to proceed in the game.
There is one space knight on each of the three planets (Jungle, Ice, and Fire), and each will provide you with a weapon to fight the mechanical creatures there. Jungle Planet (X-15 Y-15) - Sir Cador - Laser Lance Ice Planet (X-73 Y-83) - Sir Gawain - Force Shield Fire Planet (X-83 Y-20) - Sir Peleas - Ice Arrow
On the Fire Planet, you get it from Sir Peleas when you reach the bottom of the interior of the volcano. (see related question)
The arrow is at the castle