Hello Karen,
If your Windows 10 device doesn’t have enough space for the update, it will ask you to connect an external drive to extend the space on your hard drive temporarily while the update is being installed.
To resolve this, you can free up space on your device by deleting nonessential files if you don’t have an external storage device or don’t want to use one. Please visit this article on how to free up space to install the latest Windows update because it has an easy guide to troubleshoot the issue.
You can also try this article on how toFix Windows Update issues by visiting this guide to download the Windows Update Troubleshooter. It can fix errors you might encounter while downloading a new update.
Hope this helps and let us know if you have any questions.