Where Your Files Reside
For most of our customers, what you see when logged into your FTP account is located at /home/username/. However, this is not always the case for every server. For some customers on specific servers the files are located in /home2/username/ or /home3/username/.
If trying those combinations does not work, you can use the script file linked at the bottom of this answer. To get started:
Download the compressed file and unzip it (decompress it)
Note: get the file here https://www.asmallorange.com/extras/whereami.zip.
Upload the file into your 'public_html' directory via FTP
Visit 'http://yourdomain.com/whereami.php' to see where the file is located and figure out your path from that location
Where to Upload Your Files
Each cPanel account has a home directory (for shorthand, we notate it like ~/). Within your home directory, you have a number of directories (folders) with different purposes.
public_html (aka 'www')
To upload your website files, you'll want to use the ~/public_html directory. There is also a directory called ~/www, which is merely a link (shortcut in Windows parlance, or alias to you Mac users) to '~/public_html'.
If you are using an FTP client to upload files, then it may ask for a folder/directory when you put in your login information. This directory is not required, but you can enter 'www' or 'public_html' if you wish. Either way, you need to change to that directory in your FTP client, and then upload your files.
cPanel File Manager
If you log in to cPanel and click on File Manager, you'll see a folder listing that looks similar to the what you would see when using an FTP client.
Click on the folder icon for www or public_html (don't click on the name, just the icon) to move inside of that folder
Click the Upload Files upward-pointing arrow
Use the browse buttons to select files to upload