Editing Blueprint Interfaces
Blueprint Interfaces are edited the Blueprint Editor. Since you cannot create your own variables, graphs, or components, the process of Interface editing differs greatly from the process of editing standard Blueprint Classes.
When you first open up a new Interface, the editor looks like this:
If you have just created your Interface, you will see that the Editor has created a new blank Function for you named NewFunction_0 and it will be highlighted for you to rename it.