sterndata on "Changed url and now everything is locked"

Just recived the website http://reykjaviktravels.com .

I changed the url to HTTPS://WWW.reykjaviktravels.com ,

Both wordpress url and site url.

Not I can not access the site and not the /wp-admin.

I am locked out and can't do anything.

I have a backup saved on my computer but don't know what to do.

I am not good at this programing thing need all the help I can get.

I am using only the online dashboard if that matters.

I changed the url to HTTPS://WWW.reykjaviktravels.com

Reset the URLs in the wp-config.php file:
See https://codex.wordpress.org/Editing_wp-config.php#WordPress_address_.28URL.29 and put them back to http:// instead of https://

IN order to run your site as https, you need to have installed a valid SSL certificate and configured your server to accept https traffic.