There is no guide for this game yet. But apparently it is EASY POINTS! 

Coastal Guardian - 10 points

Fend off the Telmarine ships.

Cair Paravel Custodian - 10 points

Rescue Queen Susan's Horn from the throne room.

Gigantic Allies - 10 points

Defeat the archers that are threatening Cair Paravel.

Stemming The Telmarine Tide - 10 points

Seal the doors and escape Cair Paravel.

A Pyrrhic Victory - 35 points

Escape Cair Paravel with Queen Susan's Horn.

Siege Weapon Destruction - 10 points

Use the giants to destroy the catapults in Cair Paravel.

Cave Dweller - 10 points

Work through the cavern to find a grapple.

Father Christmas' Gifts - 10 points

Explore the treasure rooms and find the Pevensie's clothes and gifts.

River Retrieval - 10 points

Rescue Trumpkin from the water.

Feral Forest - 10 points

Find a safe route through the woods.

Ruins Revealed - 35 points

Complete the entire Cair Paravel Ruins area.

Gryphon Flight - 10 points

Use gryphons to take out the turret sentries.

Silent Sentries - 10 points

Defeat the sentries along the castle walls.

Liberation - 10 points

Rescue Cornelius from the dungeons of Miraz's Castle.

Bell Tower Rescue - 10 points

Rescue Edmund and Trumpkin from the bell tower.

Surreptitious Arrival - 35 points

Complete all of the areas within Miraz's Castle Infiltration.

Small Is Big - 10 points

Reach the control room to let the Narnian army in.

Portcullis Peril - 10 points

Open the portcullis and let the Narnian army in.

Courtyard Pugilist - 10 points

Battle through the courtyard to get to Peter.

Tyrus The Brave - 10 points

Reach King Miraz by scaling the castle terraces.

Stable Rescue - 10 points

Rescue Cornelius from the stables in Miraz's Castle.

Valiant Escape - 35 points

Complete all of the areas in Miraz Castle Assault.

Approach To The How - 10 points

Complete the Approach to Aslan's How area.

Lucy's Escape - 10 points

Help Lucy escape on horseback from the How.

Smash The Pane - 10 points

Defeat the White Witch.

Miraz Vanquished - 10 points

Defeat King Miraz in the combat ring.

Defense Of The How - 35 points

Successfully complete all areas in and around Aslan's How.

Conqueror Of Lord Gregoire - 10 points

Defeat Lord Gregoire in battle.

Into The Cistern - 10 points

Find a way into the secret cistern in Aslan's How.

A Cunning Plan! - 10 points

Collapse the battlefield by destroying the support pillars.

Conqueror Of Lord Glozelle - 10 points

Defeat Lord Glozelle in the Cistern.

Surprise Attack - 10 points

Rescue Prince Caspian on the battlefield of Beruna.

Nature's Vengeance - 10 points

Take control of the trees and destroy the Telmarine army.

Aslan's Gift - 70 points

Rid Narnia of the Telmarines

Junior Treasure Hunter  - 10 points

Open 10 bonus chests in single or co-op play.

Treasure Hunter - 25 points

Open 25 bonus chests in single or co-op play.

Senior Treasure Hunter - 50 points

Open 50 bonus chests in single or co-op play.

Treasure Hunter Extraordinaire - 75 points

Open 75 bonus chests in single or co-op play.

Treasure Meister - 100 points

Open ALL bonus chests in single or co-op play.

My Body Is A Temple - 40 points

Upgrade your health fully in the game.

Find A Friend - 15 points

Play 5 missions in co-op play.

Fun With Friends - 40 points

Play 15 missions in co-op play.

Caspian's Retribution - 20 points

Seek vengeance from 200 Telmarine soldiers.

Girl Power - 20 points

Defeat 75 Telmarines as Susan.

Remarkable Rodent - 15 points

Defeat 25 enemies as Reepicheep.

Trumpkin's Delight - 15 points

Defeat 50 Telmarines as Trumpkin.

Equestrian Antics - 10 points

Defeat 20 enemies while on horseback.

Centaur Charge - 15 points

Charge around as the centaur and take out 40 Telmarines.

Reply To All - 15 points

Issue a reply to 100 Telmarine enemies in the battle.

Salubrious Slumber - 10 points

Send 10 guards to sleep with Cornelius' sleep potions.