Writing a simple function in Swift is easy and straightforward. All you need to do is define the function, provide the parameters, and write the code that will be executed when the function is called. To define a function, use the keyword “func” followed by the name of the function. Then, provide the parameters in parentheses. After that, write the code that will be executed when the function is called. Finally, use the keyword “return” to return the result of the function. With these steps, you can easily write a simple function in Swift.