I am trying to extract with winrar. when I extract it, it gives me another BSA file...
Erm .. You dont need to extract any BSAs', unless you are just curious about what is contained. The game loads its BSAs fine without having to turn them into loose files.
But if you are just curious, or want to make your own replacers and thinking about making your own mods ...
I mentioned they are similar to zips, but that was just to give an idea of what they are - However WinRAR and 7zip (or even WinZip) will not extract them, you need a special utility to do that http://skyrim.nexusmods.com/downloads/file.php?id=247
Using BSAOpt you select your source BSA
And then select a destination folder (preferably a temporary one outside of your game installation)
Then it will extract the BSA to that folder.
If you ever get to the stage where you want to use BSAOpt to make a BSA from a folder of loose files, be sure to also check Skyrim in the Game menu (BSAOpt defaults to Oblivion format BSAs, when automatic is selected .. and so will create BSAs which will crash Skyrim when it tries to load them).All of the above though should not be needed for your original problem
- You said the mods you downloaded needed to be put in the textures folder - I presume the mod in question is assuming you already have other mods installed which have previously made a textures folder in data\
All you should need to do from the mod you have downloaded is extract its files, and place the extracted textures folder into your data folder.
Or if the mod has a bsa the bsa just goes into your data\ folder - No need to do anything else with it.
Maybe I have confused things by expanding on the subject to broaden your knowledge about modding skyrim, but the mod authors instructions (you should read them for each mod that you install carefully) should be enough to install it correctly.
We cannot currently help any further with the information you give in your first post "some mods" and "it" .. No idea what mods we are dealing with.