First, you have to learn to use the CS.

It's not easy and there is no simple explanation, You really do need to do the beginners tutorial in the WIKI. I know the beginner tutorial doesn't tell you exactly what you want to know, but without really knowing that information, you will not be able to progress to what you do want to do.
The beginning tutorial teaches what you need to know to get around and find the different parts of the CS, how to manipulate objects and other things in the game, and most importantly, how to get your changes into the game. If you are not willing to spend a lot of time learning how to make mods,

just download the ones you like and enjoy the game.
If you are willing to put in a lot of time and endure the frustration of using the CS

, Welcome to the ranks of Oblivion Mod makers. The first time you see someone actually download and use one of your mods makes it all worth while.