Clarify instructution for exercise `pilot`

subjects/pilot/README.md

@@ -2,7 +2,11 @@
 
 ### Instructions
 
-Append to the code below what is needed so that the program compiles.
+- Create a directory called `pilot`.
+- Inside the directory `pilot` create a file `main.go`.
+- Copy the code below to `main.go` and add the code needed so that the program compiles.
+
+> Note: You can only add code, not delete.
 
 ### Usage