How do I close BT Cloud set up box from my desktop

Great! Thank you. Nice background image, btw.

I'm assuming you have already tried shutting down your Mac, and then, booted it back up and this window re-appeared ... correct?

If so, it would most likely be one of your Mac's "Login Items."

You can check by going to System Settings > General > Login Items

Look under the section, titled: Open at Login. Check to see if BT Cloud Desktop is one of the items listed. If it is, select it, and then, select the "minus" key to remove it.

Are you running any VPN, Anti-Virus, or Cleaning apps?

We need to see what all is running, a report from this will not display any personal info...

Using EtreCheck - Apple Community

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info. Give it Full Disk Access.

https://www.etrecheck.com/

Give etrecheck Full Disk Access before running.

Thanks for Old Toad’s etrecheck instructions…

Slow iMac 2017 - Apple Community

https://discussions.apple.com/thread/255738751?sortBy=oldest_first

Of course they did. ;)

Have you tried selecting this set up app, and then, choose "Force Quit?" Try "Quit" first, then "Force Quit."

Could you also take a screenshot so that we can see what you see?

Are you running any VPN, Anti-Virus, or Cleaning apps?

We need to see what all is running, a report from this will not display any personal info...

Using EtreCheck - Apple Community

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info. Give it Full Disk Access.

https://www.etrecheck.com/

Give etrecheck Full Disk Access before running.

Thanks for Old Toad’s etrecheck instructions…

Slow iMac 2017 - Apple Community

Uninstall both.

You're very welcome!

Great troubleshooting! I'm glad you got it worked out.

You're welcome... did you get it accomplished?