First, this is the programming assignment for Mueller's class (not a lab).
When you write the getInteger method, you are writing a general purpose method that will only be call once in this program, but we might use in another program.
The parameter which is a String is to allow the user to pass the prompt for the input to the method. That way if we were to use the method again with a different prompt, we would just change the actual parameter passed to the method, rather than the code within the method itself.
The idea is that in the main method you will call the getInteger method and store it's return value in a statement like this (though your variable names may be different).
int numYears = getInteger(console, "Number of years: ");
Similarly, you will write a getDouble method which you will call four times. One of those calls might look something like this:
double annualRate1 = getDouble(console, "Yearly interest rate: ");