can’t get my monitor to work with my macbook

Hi all

I have a macbook. Bought it about a year ago. Bought a Viewsonic
VX1935wm monitor. Got the adapter. Plugged it in. I can see my
background and can get my mouse to work, but can’t see what is on my
desktop, inlcuding my drive! Althought the 1440 x 900 resolution was
not available on my laptop, it was available on the viewsonic screen. I
selected it. that is as far as I have gotten. so far can’t use it. Any ideas?