The number 1 thing you need to know before uploading any files to your website is the location of your public folder. With cPanel you have the ability to upload hidden files to your server, making them inaccessible via the browser and therefore, anyone but you. In order to make your files public, you will need to upload them into the "public_html" directory, which is in your root user folder. All files located inside your public_html will be viewable to visitors.
The main file seen on a website is the index file. There are many different extensions available for the index file, but you'll most commonly see index.html or index.php being used. To make sure no one can see files you don't intend them to see, upload an index.html file into your public_html directory. If you are not ready to upload your website, you can simply put a note in the index.html (no html necessary) that says "Website Under Construction." This will stop anyone from viewing your files while you update while leaving them a note.
Uploading your files via FTP is different for each FTP client, so it's a bit difficult to explain this. However, the File Manager is the same across all cPanel accounts, so this example will instruct you in adding an index in the public_html with the cPanel File Manger. Both FTP and the File Manger can be used to manage the files on your website. The difference is that an FTP client is for moving files between your computer and the server only, while the File Manager will allow you to upload files, download files, and edit files in realtime.
Open your control panel (http://yourdomain.com/cpanel) and scroll down to the File Manager. You will see two options for File Manager, one labeled Legacy. Choose the Legacy File Manager and then choose Home Directory. This will open up your File Manager in your home user directory where you have access to all the files on your account. The novice user should not touch any files or folders located in this directory.
You should see a list of folders including access-logs, etc, mail, public_ftp, public_html, tmp, and www. The www directory is just a link to your public_html directory and they can be used interchangably. None of these folders should be editted in any way, including changing permissions or deletion.
To enter the public_html/www directory, simply click the icon next to public_html. Do not click on the word. Clicking on the icon shows you the contents of your website that is available to the public. The only folder that will be listed originally is the cgi-bin, which is where you place CGI files. This folder has become mostly obsolete through the years and very few people still use CGI (since PHP is much more versatile). Just ignore the cgi-bin.
At the top of the File Manager in the center you'll see a link that says Create New File. Click this, then look on the sidebar on the right. It will ask you what to name your file. For our purposes here, we'll name it index.html, then choose Text Document and click Create. This will create a file in the left frame called 'index.html'. To edit this file, click on the words, then click Edit File. It will ask for character encoding, but just leave it at us-ascii and click Edit.
In this file simply type: This site is currently under construction. Please come back later.
Then click Save Changes.
Open up your domain in your browser to view the new index you've just put up. You're now hiding any files you may put up. This is important because anything available to others for viewing is also available for them to take, and you don't want anyone snooping through your files.
Here is a video tutorial to walk you through it: