A: 

You need to store a collection (array / vector etc.) of coordinates that is added to each time the mouse button is pressed - and then when rendering in WM_PAINT, draw an image at each of these locations.

Will A
i thought of that. the problem is how to store the coordinates in array when the program runs i don't know how many times the left mouse button gonna be down
Ramiz Toma
That's where vector comes in - see http://msdn.microsoft.com/en-us/library/9xd04bzs%28v=VS.80%29.aspx.
Will A