okay. look on the back of your guitar. if it has like something with holes that has screws on it, you should unscrew that carefully and then loosen the strings till they come off and pull them from the back. you might need a wire cutter to cut the ends of it so itll go through. if you do not with to remove strings but just replace them, then remove the broken string if you havent done so and insert the proper string thrugh the back. the strings go like this for a right hander if he/she was holding the guitar properly:

e
A
D
G
B
E

make sure you replace the strings with the proper string. on all the string sets i buy there is a letter and a gauge number next to it. you dont really have to pay attention to the gauge but make sure you're replacing with the proper letter. when you're done, tighten the string and screw back the thing on the back of the guitar.

if your guitar doesnt have that thing on the back then you have to replace the strings a different way and i dont know how to do it that way cause ive never owned a guitar that doesnt insert strings at the back. hope that helps. all fender or like electric guitars are like this.