First of all you should select the brush, which you want to use. Press to any cell and choose any image you want. The program automatically set it to a brush size. Now, if press left mouse button, you can draw on a white canvas. To make texture more tile, you should go from left side of the screen to the right - just move the mouse in one direction - the program will take mouse to the right place. You can load 10 brushes. Then, choose the brush with simple clicking on it.
(!) You can delete the drawn objects with right mouse button.        

You'll see this window. Choose images from your disk here.