First, it said your function will receive a list of commands. For your function to receive something, it is best to use parameter(s) in the function definition. Add a parameter which will be a placeholder for the string that will be passed into the function. To make it clear what the string represents/contains, I would name this parameter commands.
Second, inside the receiver function, you will then iterate over the string passed into it (the argument). Currently, you are iterating over a variable named rover I do not see a rover variable anywhere in your code, so I assume it is some global variable? It really does not matter, because the instructions do not mention iterating over the rover variable to accomplish anything. Focus on iterating over the commands string passed into the function.
Third, inside the for loop, your if statements should be checking if the current string character being iterated over in the commands string is an ‘f’, ‘r’, or ‘l’, Reference the previous paragraph for what the string is. If these are the only three possible characters, you can use one if statement, one else if statement, and one else to call the applicable functions (goForward, goRight, or goLeft). Do you know how to reference a specific character in a string? If not, you should refer to the FCC challenge named Use Bracket Notation to Find the Nth Character in a String.