This has not changed since very eary versions of FileMaker.
Enter layout mode. Click the button tool.
Draw a rectangle where you want your button.
Select "Perform Script" in the button setup.
Click "Select" and select the script that you want your button to perform.
You can also enter layout mode, select an existin objects such as a graphic object, layout text or a field and then use Button Setup from the format menu to turn the selected object or objects into a button.