To get this trophy you just need to build a Nether Portal, enter the Nether and kill a Blaze. This will drop a Blaze Rod. Pick this up to earn the trophy.
The easiest method I have found is to start the tutorial world on Peaceful difficulty, find the Nether Portal (located in a house just up some stairs from the starting area)
Dig around in the Nether until you find the Blaze Spawner in the Nether Fortress (make sure you have a sword in your inventory), then save and quit the world.
Load the world back up on Easy difficulty and kill a Blaze when they spawn. Pick up the dropped Blaze Rod and the trophy is yours.