A hi hat comes with two cymbals one for the top and one for the bottom and is above the snare is has a platel where you can open and shut the two you can open just a littile and get a diffrent sound so miss around with it and see what you can do.
When tightening your drum cymbal you should always make sure you dont over tighten. Leave some slack so that the cymbal has room to move, when you strike them. In this drum lesson link you will find info and example images on htting your cymbals.