URL /wp-admin/install.php was not found on this server.

I’m trying to do a first-to-last installation all by myself. (a longtime WordPress content user/editor but not experience actually installing on the back end)

I’ve gotten to the installation point, where I used “Transmit” to upload WordPress files to my new website (via ftp transfer). My next step is to run wp-admin/install.php, but when I do I get the error message saying: The requested URL /wp-admin/install.php was not found on this server. I think I uploaded the files into my root directory properly, but maybe not…?

Can someone help me understand how I know that I uploaded the files correctly to my root directory? Or trouble-shoot why I can’t run install? Thanks in advance for your help!