Assuming you are referring to the Mini Steam Iron SF-717 from Steamfast:
Fill the tank with water using the provided measuring cup. Make sure not to overfill as this can lead to water leaking out during use. Plug in the iron and wait for the power light to turn green, indicating that it is ready for use. Set your desired steam level using the knob on the front of the unit. The higher the setting, the more steam will be produced. To start steaming, press and hold down the steam button on top of the iron. Once released, press and hold again to continue steaming. Use caution as too much steam can cause fabric damage. To stop steaming, press and release the steam button once more then unplug and allow your iron to cool before storing away.