There are a number of helpful threads on this:
http://wordpress.org/support/search.php?q=dreamweaver
In 1.5.x, your *home* page is either the index.php or home.php in your active theme’s directory. Also note that most themes are broken up into various templates, so that your document head may be in header.php, the sidebar in sidebar.php, etc.
Lots of info on WordPress themes:
http://codex.wordpress.org/Using_Themes
One piece of advice– work in codeview, and don’t bother with the preview. Since theme files are “pieces” of html pages (generated by php) DW can’t display them properly. Best to edit, upload, then test. If the page doesn’t work, use “view source” to troubleshoot.
