direct link to create a template http://www.auctiva.com/listings/template_createcustom.aspx
once you have custom templates saved on system, when listing an item, click the select template link then in top left box on template page highlight "custom"
on a side note, you can create profiles to use when listing and specify which template to use, so if you make a few profiles you can list an item using profile in just a couple of mins. (however long it takes you to do description)
for custom templates, the auctiva tags are available on the left hand side. just click which type of tag you want and it autoinserts it into your custom template. if there's a tag you want that's not in there, the complete list of tags is at http://www.auctiva.com/listings/template_tags.aspx
to convert a custom template to be auctiva compatible, just use that list of tags to match up what tags you need and replace SD/IF tag with corresponding auctiva tag.
hope that helps
donna, wahm, and magie all 3 have extensive experience in converting SD/IF templates to auctiva templates. So if you need more help, i'm sure they will be happy to help ya.