I'm a beginner, I just got terraria on xbox 360 and I've heard that I can craft Cactus Armor but have no idea how to do it. Can someone explain it to me?
Get 75 pieces of cactus, which are easily found in the desert biome. Use a workbench to craft each piece of the armor set.
Take a look at the official wiki for more info. It's a great resource when you're trying to learn about the game.
Find the desert biome and swing at cacti with an axe till you get to 75, less with not get you the full suit, and got to work bench and look for the green suit in the crafting area.