Photoshop will create the files you need for the web gallery. One of the files is called "index.htm", that will be the homepage. If the page you already have on your site is called "index.htm" then delete it (or back it up) using Filezilla. Now go to the folder that photoshop created and upload everything in that folder (not the folder itself though) to your site. On your site, you should then have your index.htm, the other pages Photoshop created (these will be .htm files, by default Photoshop calls them "index_2.htm", "index_3.htm", "index_4.htm", etc.), plus the folders containing the images, pages and thumbnails. When all those are uploaded to your site, enter your site's address into your browser and the "index.htm" page should appear.