shaun Mosswood

I have bought some sand/pebble textures to put along the shoreline of my island and im having difficulty, Ive tried to drag and drop and this dosnt work, im sure i dont upload the texture to the terrain window in the estates menu otherwise all the land will change at that level. Please excuse my ignorance but how do i go about this. I have been told i may have to change the texture into a prim ?