The data files that constitute your web page are stored in two locations, namely (a) in a folder on your hard drive and (b) on a server owned by a website hosting company or by your service provider. At each location the source code for the page itself will be in a folder named [mywebsite], while any graphics on the page (e.g. .jpg or .gif files) will be in a subfolder named '[mywebsite]/images'.
Making changes to a web page is a two-stage process as follows:
1. In location (a), amend the source file(s) as required. Format changes normally demand some knowledge of website source-coding and the use of web-authoring software, while appropriate specialist software is needed in order to make changes to graphics. However, simple text changes (e.g. to correct typos, etc.) can be made using nothing more complicated than Notepad. Don't forget to save the amended file(s), taking care to save any amended graphics file(s) to the 'images' subfolder.
2. Upload the amended file(s) to the appropriate folder or subfolder at location (b), using an ftp (file transfer protocol) program. To do this you'll need to know the user ID and password used by the person who set up your website in the first place. (If you're lucky, the ftp software used originally may still be on your hard drive, in which case the user ID and password may not need to be entered again.) For each amended file the software will warn you that a file with that name already exists on the server, and will ask whether you wish to overwrite it — which you do, of course.
Freeware programs are widely available. I use:
— for web authoring: click here.
— for ftp:
Hope this helps.