Theme Installation Not Working, Please Help

I installed WordPress, then I uploaded via FTP a new WordPress theme, “Winterplain”, placing it in my ‘themes’ folder.

Then when I went to activate it from the WordPress admin panel, I’m getting my parent directory showing up instead of my blog at this URL: https://leakbird.com/

Now when I try to return to the default theme, it doesn’t even work — I only get my parent directory showing up at the URL.

Please consult me on what file I might be missing or what I’ve done wrong.

Thanks and sincerely,
Ben