The reason for the vertical space is the default margins. I would recommend using the
geometry package for changing the page geometry.
[showframe] option to the geometry package you see that the text is actually already at the top of the page, but the page has a margin before the text starts (The gray bar at the top is the top of the page):
To see which dimensions you need to adjust you can use
\layout from the
layout package. So, with the following:
you get a nice image on page 1 that shows the various dimensions. From the top of this page you see:
So the dimensions you are interested in are (2) and (6). From the bottom of the page we see:
Hence you need to adjust
1.0in is added to the dimension specified in
\voffset, I set that to a negative value.
So, for instance setting this to: