The first thing you will need as you make a piston in Minecraft is to gather resources you are going to need to make a piston. Examples of these are 2 blocks of wood, 12 cobblestone blocks, one iron ore, one slime ball, and one redstone. Depending on the version or edition of Minecraft you are using, you will need to create wood planks.
The next step to take is to exit the crafting menu. Whether you are using a computer, console, or PE, all you will need to do at this stage is to open your crafting table. After which you create a furnace and place it on the ground. Once you are able to place it on the ground, try to open the furnace. You will also need to create an iron block, after which you leave the furnace and go back to the crafting table.
This stage is where you will create a piston. Create a piston by ensuring that each square on the top of the crafting table contains a wood plank box. The middle square should contain the iron bar, and the Redstone right under it. Finally, the rest of the squares should be filled with cobblestone.