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Please post the full text of the compiler's error message that shows what symbol can not be found and what source line in the code the error is on.

There are lots of code samples on the forum or Google.
Do a search.

Change the x,y values in the fillOval() method to use variables instead of hardcoded numbers.
Then change the values of those...

Change its x,y location so when the paint method is called it will be drawn at a new location.

You will need to use a keylistener or key binding so the program will know when one of the keys is pressed and can react to it.