If you're learning to play the violin, it's important to know how to string it yourself. In the beginning, your teacher may do this for you, but getting to know the mechanics of your instrument is part of what it means to be a musician. When trying to re-string your violin yourself for the first time, remember to always handle your instrument gently, since there are many small parts that need special care. Having said that, you may need to use a bit of muscle to tighten the pegs after you've strung the new string. Be careful in all you do with your instrument. Here's a step-by-step guide to replacing a string on a violin. Good luck!
Gently loosen the peg that's connected to the broken string until the string is lax.
Gently release the other end of the string, which is connected to the tailpiece near the chin rest. Undo the broken string and discard.
Insert the small metal ball at one end of the new string into the tailpiece. Poke the other end of the string through the hole in the peg. Pull this end through the hole no more than one inch.
Gently but firmly tighten the peg, taking care to wind the string around the peg neatly. You'll feel the string begin to get taut. Push the peg into the scroll as you tighten it.
Make sure that the string is resting in its groove on the bridge, and also in its groove at the base of the scroll. Keep twisting the peg tighter, while plucking the string to hear it return to its correct pitch. You'll need to tune the violin a few times to center its pitches again. You may also use the violin's fine tuners.