An FTP (file transfer protocol) program is just an easy way to transfer files to-and-from your computer and a server where your web site's files reside.
The server control panel (cPanel, Plesk, etc.) is a set of graphical programs that allow you to interact with your web server. The one you have will vary depending on who your web host is. If you can log in to your server control panel, that's probably the easiest method for your skill level since you won't have to worry about trying to connect to your server; that's already done for you.
Typically, in the welcome email from your web host that they sent you when you signed up for your hosting account, they will have given you the URL (web address) and login credentials for your server control panel and their support ticketing/billing system. If you don't know how to access your server's control panel, you'll have to either refer to that email, look at your web host's support pages on the web, or contact your web host.
You can probably skip the step of looking at the error logs, but to follow the instructions in the Master Troubleshooting Guide, you may still need file access to your server, and you'll eventually need to learn this, anyway, unless you have a friendly neighborhood computer geek to help you out.