i have tried that but it always says object doesn't have a gui texture component
You need to add a GUI Texture component to the GameObject.
You can create a new GUI Texture:
Unity Main Menu > Game Object > Create Other > GUI Texture
Or add a GUI Texture to an existing object:
Unity Main Menu > Component > Rendering > GUITexture
You should also look over the GUI Texture docs in Unity and play with it a bit in the editor to get the hang of it.