You need to create a new world in your Minecraft game and then click on the "Create New" button in the bottom right corner of the screen. Then you need to click on the "New Game" button in the bottom right corner of the screen. Then you will be able to see an option called "Super Mechs" at the top of your screen. Now choose which type of mech you want to create, weapons and armor, etc., then click on it and you will be able to create your own mech!