Okay, first you start Texmod.
There you can find some Tabs :

- Package Mode
- Logging Mode
- Package Build

Now you press on the second tab called "Logging Mode".
You will find a black frame with a little folder in it on the left upper side,
click on it. A window will appear. Choose the Game .exe (in your cane TESV.exe)
file of the Game you want to edit.
Under the taskbar there are some options.
tab :
-Draw Control and Texture Info
-Show Texture on upper left Corner
-Replace Texture (with a green Texture)

in your upper left corner you will see, how many textures are loaded, and which you have choosen, to go forward press "+ (plus)" and to go backwards press "- (minus)", the texture will be replaced with green texture, you can output the texture with bmp, png, jpg,

you will also need photoshop to edit the textures itself

because im not good with explaining here's a video
(works the same with skyrim)
http://www.youtube.com/watch?feature=player_embedded&v=EKHse9Smcw0

here's some pics how i edited breezehome and solitude, well im not good with photoshop