Firefox desktop drive won't eject

Totally new to mac,(bought it 3 days ago). Downloaded firefox and ran it off of the disk image, (now I know that was a rookie mistake). So I trashed everything I could, but it won't let me trash the "desktop drive icon" nor the disk image, evidently because the "desktop drive icon is in use" I re-downloaded and installed firefox the correct way and that "icon" and image were easily trashed, but I still have the original "icon" on the desktop that will not eject, and the disk image that is not trashable. Help!!

Quit FireFox. Then you can eject the disk image.

It sounds like the Firefox in the Disk Image is running still. Look down on the Dock and see if you see a Firefox icon with a up arrow under it. If so Right or CTRL Click and select Quit. Otherwise reboot the Machine.

Firefox is not running any longer. Everything was trashed except the disk image and the drive icon.

Did you try rebooting the machine?

Will try that and get back to you.