Changing guitar strings without tools can be a bit tricky, but it's definitely possible. You can use your fingers to loosen the strings, and then carefully pull them off the tuning pegs. To put new strings on, you can use your fingers to wrap the string around the tuning pegs, making sure to wind the string in the correct direction (see next question for more information on string windings). Once the string is on the peg, use your fingers to tighten it by turning the peg. Repeat this process for each string.