Any help would be appreciated...

We've recently upgraded to Filemaker server 11 (not advanced) and Filemaker Pro 11 from version 7, so I have no experience with the web publishing.

I've used the PHP 'site assistant' to create a site, but now I want to make some alterations, ie. add a supercontainer for images and change the layouts a bit. But I can't figure out how this is done, I've read all the documents from filemaker, but none of them actually describe how to launch the PHP API.

Firstly is that the correct application to use to make the amendments I mentioned? or should I use something like Dreamweaver?

Thanks in advance.

Just check out the manual. You will get the proper steps.

The API is a the programming interface - it's just a series of PHP libraries that ease communication with FileMaker server.

To actually make modifications to layouts etc., deal with the .php files in dreamweaver or notepad.... there's nothing particularly special about the files the site assistant generates.