Extension

Hello All,

I am building an extension but need some help. It says here on the website that extensions are installed together with the FA. But when I install and check the checkbox it doesn't install any extensions/modules.
So I can't find any extensions to look how I should build one.
I have found some posts on 'how to' but they don't give enough information on 'how to for dummies' .......
I am using version 2.3.10 on Ubuntu

MySQL version >=4.1     Required     5.0.75-0ubuntu10.5     Ok
PHP version >=4.3.3     Required     5.2.6-3ubuntu4.6     Ok
Http server type     Info     Apache/2.2.11 (Ubuntu) PHP/5.2.6-3ubuntu4.6 with Suhosin-Patch     Ok
Server system     Info     Linux

Does someone have a example of a module?
I need to have an extra button on the tab: SetUp and then in the square: Miscellaneous.
That button should call a php page which will make a xml file, the php page is ready and the xml is build when the page is loaded. So all that is working. I even know a little ajax to call the php page from javascript.

Please bear in mind that I am not a senior php programmer.
(yet)

Thanks in advance,
Brian