I have created several html files. Can I upload them into my website using SiteSpinner and then also update them in SiteSpinner if I want to rearrange some things on the pages?
If you created the html files in SiteSpinner, then you can upload them using SiteSpinner. And if you make page changes in SiteSpinner, then you would just upload the changed files to your website again.
If I created them in a different program, can I open them in SiteSpinner? Can I open html files in SiteSpinner or do I need to convert them to .ims files?
SiteSpinner is a WYSIWYG (what you see is what you get) editor, so html files cannot be edited in SiteSpinner. Though you may be able to make them into an .ims file if you create html code objects in SiteSpinner.
If you already have the html files ready to upload, then you could just upload them through the webhost account area file upload page.
Uploading & Updating HTML Files