how do i update my website?

Answer 1

This completely depends on how your website is hosted.
Usually when you purchase a hosting plan from someone they will give you explicit instructions on how to log on and administer your account. Once you log on, there is usually some sort of graphical interface to upload files.

If you are talking about one of the 'free' website places, each one is slightly different, but they all have some sort of way to upload files or edit the page directly in either an online text editor, or through a graphical interface.

"how do i update my website" is way to vague to provide more detailed instructions.