Welcome to the Ranch
I have moved you to a more
appropriate location, and edited your post to remove the red text, which some people can't can't read, and added
code tags, which usually make the code look nso much better. Unfortunately in this instance, they simply show how very badly that code is formatted
The message about the exception is clear. But null pointer exceptions don't occur where the error is. The real error is in line 9. Have a look.
Don't extend JFrame. Don't make those components fields of the class. Make them local variables. Don't call
setVisible() from the constructor. Call it in a method. Don't give a JPanel FlowLayout, because it has that layout as a default. I don't like flow layout myself; I don't think it is any good.