401 error when clicking on any uploaded media

Hi all, apologies if this has been asked before.

WordPress blog all set up, works wonderfully. Only issue I have is with any media uploaded. Docs/images upload and attach to page fine, but when a page is viewed, and any document, etc is clicked, it does not open, but displays:

Server error
401 – Unauthorized: Access is denied due to invalid credentials.
You do not have permission to view this directory or page using the credentials that you supplied.

I’m not too knowledgeable on server-side issues; do I need to change the permissions of my media folder?

If anyone could take the time to lend a hand, that would be great.
Many thanks in advance,

Amber ??