The DNA plots are accessed from the Graph menu (see the section called The Graph Menu). When a graph is turned on it is locked to the overview window, so it will follow the overview window when the overview is scrolled. It will also automatically change the viewing scale to match the scale of the overview window. The vertical scrollbar to the right of the graph controls the window size of algorithm.
The feature plots window (see the section called Show Feature Plots) has a horizontal scroll bar that sets the position of the plot in the feature. As with the DNA plots, the vertical scrollbar to the right of the graph controls the window size of algorithm.
Note that clicking the left mouse button on the plot will show the base or residue at that position. Clicking the right mouse button will pop-up a menu. The menu contains a toggle which controls whether the graph is scaled and some menu items which allow the maximum window size to be set.