@stewie911said How do I turn it into a Queen or castle ?
Default is a Queen when you submit the move. If you want a different piece there is a drop down menu near the submit button, but it doesn't immediately jump out at you.
If you have played on the live chess here, you may have noticed promotion is a little different, with the promotable pawn turning into a box of all available pieces for quick selection.
This will become the default in the future on the correspondence interface too, but for now, it is as @Relentless-Red described.