Anywhere you see a /classic folder, you can create a folder for your custom template. Only create folders and copy files where you need them.
This list is a bit outdated, but it will give you a general idea of what to do and where to do it. Replace YOUR_TEMPLATE with whatever name you want to give your custom template.
To create a very basic custom template (you can build from there), you need:
- includes/languages/YOUR_TEMPLATE/english.php
- includes/languages/english/YOUR_TEMPLATE/index.php
- includes/languages/english/YOUR_TEMPLATE/meta_tags.php
- includes/languages/english/YOUR_TEMPLATE/header.php (to change the logo)
- includes/templates/YOUR_TEMPLATE/template_info.php
- includes/templates/YOUR_TEMPLATE/common/tpl_header.php
- includes/templates/YOUR_TEMPLATE/common/tpl_footer.php
- includes/templates/YOUR_TEMPLATE/images/logo.gif
- includes/templates/YOUR_TEMPLATE/css/stylesheet.css
Anywhere you see a /classic/ folder, you can create a folder for your custom template. You can copy the necessary files from either the /classic/ folder, the /template_default/ folder or the parent folder.
Edit includes/templates/YOUR_TEMPLATE/template_info.php to give your template identifying information so you'll recognize it in the admin under tools->template selection.