You can view more generations of your ancestors by increasing the 'Parents' variable at the bottom of the screen. To see more generations of decendants, increase the value of the 'Children' variable. To see more cousins, increase the value of 'Others.'
There is a limitation to the tree view that only allows you to display the aunts or uncles of the selected person, not great aunts/uncles etc.
To actually 'see' more of the tree you can click on the + or - magnifying glasses to zoom in/out.