How to set up parameters in an if statement to allow me to move to a new page?

So I am trying to set up a username and password, then log in sort of deal. What I am having trouble figuring out is how to set up the if statement. So far I have it set up so if username and password are not correct, then a label displays "Username or password is incorrect." The problem is, when I click log in, no matter what it moves onto the next page. I need to stop it from moving to the next page unless the username and password are correct.

• I am using storyboard to set it up, and I have a segue created to allow me to move to the next page. I am not using .XIB files.