Can anybody explain how to open the modding stuff for civ 4 and civ 4 BtS for me please. You could PM it to me if you want to.:D

Moved to the Creation & Customization forum.

Welcome to CFC, LonZeR! :)

The question is very far reaching....

We have a more or less well sorted Tutorial section here. Some good tutorials are linked in the Tutorial Index: http://forums.civfanatics.com/showthread.php?t=236836

You should start with something simple - maybe "Adding a new Civ" or "Adding a new Unit" - both covered in the index. And maybe take a quick look at the XML 101.
Also Downloading a few simple mods - a Modular Civilzation maybe - and looking how it is done in a example should help.