well if your okay with HTML you should know how to work on those other pages. once completed, there should be a file upload tool somewhere around geocities, use that to upload the html file and you should be able to see a URL of the document. you want to copy that and use that as the URL for the link to it (probably on the index for now).
If you want a quick HTML made up, I have a free utility I made for download onmy site, you can alter the HTML's when your done. You can also alter the file itself, just please dont redistribute the altered version. I know I put the pesky little made by thing in there just to be a pain lol.
LINK