So first of all, you should have a neighbor, then your neighbor has a guitar, and then let your villain click on the guitar and then click on the option, which should be able to complete the task. The way to go to a neighbor's house is this: find a button with a map icon in the lower right corner of the interface, click it, it will show which neighbors you have, then select a neighbor's visit button (if you know which neighbor has a guitar, click that), and then you enter another town. Then just find a house with a guitar, let your little man in, click on the guitar and practice.
However, if your neighbors don't have guitars at home, I can only regret to tell you that unless you skip the task with a drill, you will be stuck (but this is actually a communication task, which has little impact on the main line)! Or you can find more friends as neighbors (depending on the game number you use, the way of making friends is different), and then find someone with a guitar.