Electric strings, like steel acoustic strings, have ball ends and are made of metal, but electric strings are usually composed of a lighter-gauge wire, and the third string is unwound, or plain, whereas a steel-string acoustic guitar’s third string is wound. (A nylon-string’s third string also is unwound but is a thicker nylon string.)
Remove the old string (if you haven't already).
There’s no big trick to this. You can cut the wire and unwind it from the post, or, if you want to save it, unwind the tuning mechanism until you can remove the string.
Anchor the string at the bridge by passing the string through the hole (from the back or bottom of the guitar) until the ball stops the movement.
The ball holds the string just as the knot at the end of a piece of thread holds a stitch in fabric. This procedure is the same for almost all electric guitars. However, there are a few exceptions, such as those fitted with a Floyd Rose mechanism.
On some guitars (such as the Fender Telecaster), the collars anchor right into the body, and the strings pass through the back of the instrument, through a hole in the bridge assembly, and out the top.
Pass the string through the hole in the post.
Be sure that the strings go into the correct slot in the nut. Leave enough slack between the bridge pin and the tuning post to enable you to wind the string around the post several times.
Some guitars have tuners with slotted posts instead of a hole. These devices also enable quick string changes, because you simply lay the string in the slot at the top of the post, kink it, and begin winding. You don’t even need to leave any slack for winding.
Kink (or crease) the metal wire toward the center of the electric guitar's headstock.
Leave enough slack for winding.
While keeping the string tight against the post with one hand, wind the tuning peg clockwise with the other hand.
This step is a bit tricky and requires some manual dexterity (but so does playing the guitar). Keep your eye on the post to ensure that as the string wraps around the post, it winds down, toward the headstock surface.
After the string is secure, cut off the excess and tune up the guitar.
The string won’t hold the tuning for very long in the beginning because it’s still stretching. After you tune them up, gently stretch each string in a few places and retune. Do this three or four times and your strings will start to stay in tune.