now in the window on the left, select the object that the texture is going to be applied to, then go into uv select mode. Then go back into the uv editor and, select image > open. use this file system to navigate your computer and find the image you want to use as a texture. ( i save my images as .png or .jpg either will work fine.)
after youve loaded the image, select the faces of your object that the texture will be applied to.(make sure your still in uv face select mode!).
then just go into the uv editor again and select the symbol that looks like two arrows going up and down right next to the lock. select your texture. you will see that your texture is applied to the faces you selected.
this is your end result. this is just VERY basic information on how to do this. im not even sure i totally understood your problem because there are many reasons that could lead to your textures not working but heres the micro tutorial for you.
Well, all you do is go into “Edit Mode”, highlight the entire model(or whatever has the black outline), copy it, size the copy so that its just slightly larger than the original, seperate the copy from the original(Ctrl-P), flip all the faces on the copy so the faces are visible on the inside, then finally take the copy into “Vertex Paint Mode”, set the color slider to black and click “Set All”. That should do it for you. If I missed something or you don’t understand something let me know & I’ll try to simplify it more & include screens.