Geocities provides editors, EZ uploading programs, graphics, everything that you could need. You'll get a password and confirmation in email, then you go to the 'utilities' page and use the EZ editor to get a basic page on the site. After that you can edit your page with their editors or follow the suggestions in the primer that I've attached. Of course any number of subpages off your homepage is normal. The basic premise is that HTML tags are placed in a text document to tell the WEB browser HOW to display the text.
Some tags allow for attributes, which is additional information such as alignment of images.
You can build a very nice page using less than a dozen different HTML tags. You will keep everything in this one directory that will ultimately be sent to the Geocities Server. Two very nice benefits occur from doing this. This is actually your homepage and the file that the server looks for when you call the URL on-line. I then use this basepage to start both the initial page and subsequent sub-pages.