If you are going to be changing multiple strings, make sure you change them one at a time – taking all the strings off a violin at once can upset the delicate structure of a violin, leading to alterations in tension and the bridge post.
To begin, start with one string – slowly start twisting the peg it is attached to, to gradually start unwinding it. Once the string is completely free from the peg end, dislodge the other end from the fine tuner’s claw. Now that the old string has been removed, you can throw it away.
Next, begin the process of fitting in the new string. Take the ball end of the new string, and hook it into the claw of the fine tuner. Then, thread this string through the peg hole, making sure you let around a quarter of an inch of string protrude from the peg end. Take it from the centre of the peg, and wind it up to the peg box’s end.
Now, start winding the peg, to slowly start tightening the string. Do not rush this process, or tighten the string too much, as it might snap and break. Instead, go about it slowly and delicately, making sure you maintain just the right balance of tension in the string, and wind it up to the perfect pitch.
Once you are done with one string, you can move on to the others, if you wish to change more than one. Finally, do not expect the violin to go back to the way it was immediately – give it a few days for the new string to settle in and adjust into space. Once it fits in, it will begin to yield the best it has to offer. However, if it still sounds off to you after you have given it a couple of days, you might consider taking the violin to a professional, for advice on how to fix the problem.