To get a Rod from a Blaze you need to be in the Nether and you can get there via the Nether Portal. You'll need to be near a Dungeon/Castle where the Blaze spawn and you'll want to have at least Iron Armour and strong weapons. Simply hit the Blaze a few times and it will die and if your lucky enough it will drop a Rod. Pick it up and you'll get the Achievement.
Here's a video I made for my channel of how to get the Achievement.