Here are some bits and pieces about Alpha and Transparency

I take it you know at least something about color channels of images. You'll also need some knowledge of nifskope, else it might be a tad difficult to follow.

This is not a tutorial, they are a few things you should consider looking at when dealing with transparency.
There are three things you need to make an object transparent:
- Check the links
- Add/modify the alpha channel of the texture
- Change the properties at Nifksope/the mesh

Check the links
Making a Mesh Transparant and Nifkope Alchemy are the two that provide a lot of info.


Add/modify the alpha channel of the texture
When you have you texture in your image editor, create an alpha channel (if it didn't already have one.) In photoshop, it'll automatically create an alpha channel when you create a new channel.
This channel has only one purpose, determining how much will be shown. The more white/bright it gets, the less transparent in-game. On the opposite, anything dark, to full black will render transparent to invisible.

Change the properties at Nifksope/the mesh
Now on to change the values at nifskope.
There are a few settings to enable transparency.
The easiest way is to use an existing decal nif, but adding an alpha- property is always the essence do the same.
4109 is really bright, unless you're using for fog or light as it says, don't use it.

Now there are a few important settings at the NiMaterialProperty (the one with the palette-sign)

(If you want to know what they mean exactly, hover over them in nifskope, or google them )
Glossiness: The higher the value, the less intense the reflection of light is, the max value is 150, no need to get above that.

The two most important settings are the Emissive and Specular Color. The brighter these get, the more visible the texture will get. I'm not sure how they react with lighting, most tests seem to give a similar result for both.

The nice part about these two last settings that you have still a bit of control after you've created the .dds file, but it's limited...and it could get ugly if used at extremes.

Your English improved drastically. Tutorial lacks a lot in my opinion. Expand it with images and go into more aspects.

It wasn't really a tutorial, rather just a piece of info.
I'll take a look at it once I've used it again, that might take a bit. But I plan to use something transparent for the forge mod, so I'll try to get some pics then .