You are now ready to hit the Burn button.
You will see on my screenshot that no disk was present. When you have inserted the appropriate disk you will see a description of it on that line.
There are still one or two choices to be made. I would recommend that you set Verify written data, then hit the Save icon at the bottom of the screen, ensuring that it becomes your personal default. For most modern drives it's safe to leave mode and speed to Auto. If you may wish to burn another copy of the disk at a later date, select Create image, which will save having to set up the burn again. Set the number of copies you want to burn, then, when you are satisfied, hit Burn.