you need a DVI to VGA adapter that plugs into the DVI port on the GPU and then connects to a VGA cable. the VGA cable connects to your monitor.
One should have come with your GPU but if not, they're super common. maybe someone around will just give you one.
There are also Displayport to VGA adapters but they're more rare and costly. The one I have doesn't seem to work very well either (the Apple one).