You can find the Trial of the Champion dungeon within Icecrown.
The coordinates are (74.0,20.1)
Pick up a Lance and equip it from a Lance Rack (found on sides of room) then get on a mount, then speak to Jaeren Sunsworn to start.
1. Grand Champions
/i Pick up Argent Lance & equip it. If fall off mount get another. Keep Defend up & use all other abilities. After joust battle be ready for melee fight. Kill Colosos first & interrupt Healing Wave. Interrupt Ambroses Polymorph.
2. Eadric the Pure
2. Argent Confessor Paletress
3. The Black Knight
/i Damages, stuns & knocks back a player. Obliterate inflicts physical damage, amount depends how many diseases the target is suffering with. Ghouls deal damage & explode, keep away from them.