How do you use a 3D printer. To use a 3D printer you first have to make you design. You make your design by going into a 3D design program. There are shapes that you can take change the size and put them together. Once you make your design and are happy with it you have to make sure that everything is connecting and there are no floating parts before you print. Once you are ready to print send the design to the printer. The printer creates you design by taking hot molten plastic and shaping in layers to you design. It does this by first drawing the shape then filling it in and it will keep going up layer by layer creating you design. If you did your design correctly it will print it after Some time. If you did it incorrectly then it will not correctly print your design. For an example if you have a floating piece then that will fall and not print how you want it to. That is how you use a 3D printer.