If it is a Texture you have already used in your model, create a new Texture and use the Copy From pop-up to select the existing Texture you want duplicated.
Or drag a second copy from the lower portion of the Resource Palette if we are talking about one which we provide.
If it is a Texture you've created for another model and you want to reuse it in a new model, open the first model file, select the Texture then use the Resource Palette's Save command to save a texture file which Strata can then load into your new model. If you save it in the program's Resource Libraries folder, inside the Textures folder in another folder with a unique name, it will get loaded and show up in a tab with that name the next time the program is launched.