If you type "ls" (without quotes) at the prompt, you'll see the files in the current directory. You may not be in the directory in which the files are located. Where the files are located will depend on your server's configuration. Hence, you'll need to look at the config file for the webserver. For Apache, this is called something like "httpd.conf", located in /etc/apache. I think there's a DocumentRoot directive in that file and the directory that follows it is where the files should go.
One location you might want to check is /var/www, I think it's common to put things in there. Change directory to /var by issuing "cd /var" (without quotes as usual). Then run "ls" to check if there's a www directory. If there is, you can cd to it (as you did to get to /var) and then list the files with ls.
For opening files with a text editor, you just put the name of the editor followed by the file you want to open, e.g. "emacs index.html" will open index.html in Emacs. Obviously that only works if the file is located in the current working directory, otherwise you'll need to use the full path to the file. There are other editors too - vi for example. Obviously I can't say which are installed on your system!