Right button mouse on selected texture node in tree. Like in first BspViewer page. Then press import texture, and choose your texture. Same work with export, but in export you choose localisation where you want export texture from bsp.
Export1 is something different.
Export1, export one selected model with texture. You have to write 1002 in text box, then press get index, after that program should print list of all models indexes. When write one of them in text box, and then you Export1, it should work.
So, you are doing it wrong. Open file, double click on filename.bsp in my program, then double click on Textures, scrool down and choose any of them(on right should appear previewed texture). Then press right button mouse on name of texture, after that should appear small window with texts, Import texture, Export Texture. I think other things are logic
when I import the texture it pauses for a few seconds if I leave the texture highlighted its still the old texture but if I click on something else then the texture I was working on again its the color I want. So I save him and I get a backup file but the "Arclight.bsp" file but he looks the same when put him in the game. Im sorry if im sounding confusing :/
I think i have it figured out.. seemingly after you save the file you have to open BSP viewer/editor again open Arclight and his texture and import the new texture again then save and I get the 'Save succesful!" box then it works.. that seems to be what works for me