This tutorial shows you how to model a bottle in Blender

4°) Make the template /texture

To prepare the textures you must have already made the seams

Alt + mouse and choose the edge, CTRL + E and chose  Mark Seam

so when the seams are done you can then proceed with the unwrap of the mesh.

To make a image you must add a second window in your blender

to add a window : click on the border of the window with your mouse and choose Split Area

Then, place the window in UV/Image Editor and add a new image ( alt + N )

return to your first window, select all vertice from your mesh and press U key for unwrap

 Export your UV LAYOUT in your computer.