Most steel-string acoustics hold the strings at the bridge with pins. Changing one string at a time keeps the neck's setup steady and makes it easy to keep track of where each string goes.
Steps:
- Detune the string until it's completely slack, then unwind it from the tuner.
- Remove the bridge pin. Use a bridge pin puller or the notch on a string winder, and don't pry against the bridge.
- Insert the new string's ball end into the bridge hole, then push the pin in with its groove facing the string.
- Seat the ball end. Keep light pressure on the pin and gently pull the string upward until the ball end catches against the plate under the bridge. If the ball sits on the tip of the pin, the pin can pop out when you tune up.
- Thread the string through the tuner post, leaving enough slack for a few neat wraps.
- Wind so the wraps stack downward on the post, and tune to pitch.
- Stretch and retune a few times, then trim the excess at the tuner.
If a pin won't seat or keeps lifting, stop and check that the ball end is properly caught under the bridge before tuning up any further.