How to upload site to server?

There are two ways to upload your web site files to hosting server - using a File Manager (or similar) utility provided by the web hosting company or File Transfer Protocol (FTP). The first method is easier but time-consuming while the second is a faster method but needs a little technical knowledge. Using the File Manager to upload files to a web hosting server
This method is applicable only if a File Manager (or similar) utility has been provided by your hosting company. The utility is generally located under the Control Panel of your account and so you need to login first. For instance, at my hosting accounts, the File Manager is displayed as an icon along with other utilities in the control panel. The File Manager icon looks like one below.

To use the File Manager, click on its icon. A new window opens and displays the directories at your web hosting account. [Refer image below]

You need to upload all website files to the document root directory which is www or public_html in the image above. Thus, all your website files need to reside in the document root directory.
If you click on the directory name, you get a set of links displayed on the top-right that let you delete, rename, change permission etc. for this directory. [Refer image below]

To view the contents of a directory, you would need to click on the small folder image located in front of the directory name. If I click on the document root directory on my web host, it displays its contents as in the image below.
IMPORTANT: To transfer files to a particular directory, you need to first migrate to it.

To upload files, click on the Upload Files link (refer the above image). This should open a form through which you can select files from your system and upload them on your web hosting server. (Refer image below)

Using FTP to upload website files on your web hosting server
Though, the online File Manager can let you upload multiples file, it is not a good option if you plan to do this for a living (ask web developers and they will tell you). Also, the File Manager does not keep track of which files were uploaded and which were in queue in case you lose the net connection.

What you need is a special service to maintain files on your web site. The File Transfer Protocol (FTP) is just that. FTP is an Internet Protocol quite like HTTP (HyperText Transfer Protocol) which you would be familiar with. Using FTP you can quickly and easily manage the files on your web hosting server and the best way to do that is through FTP programs also known as FTP clients.