Like those Oracle offers: Swing Tutorials/Threads
. There are many others covering most topics in Core Java and several beyond. Ignore the bias in the Swing tutorials towards using the GUIBuilder in Netbeans as the way to learn and use Swing. Keep learning to code Swing "by hand."
I don't know why new Swing users or budding GUI designers often think it's a cool idea to pop components in and out of their user interfaces. It's not especially pleasant to the user to have interface controls coming and going, but it also complicates the interface for little to no value that I can see. But that's me.
You'll want to check out a JFrame's default layout and where items are added to that layout by default. You can find these topics covered in the JFrame API or in the Oracle tutorials.