Right-click the chart for the context menu, or open View > Graph on the main menu bar for the same set of controls. Most settings are per-tab and are remembered between sessions. To set the values that every newly opened chart starts with, see graph options in Preferences.

Pause freezes the chart in place; new samples stop arriving until you turn pause off. The data is still being collected behind the scenes, so when you resume the chart will jump forward to the current time. Use pause to study a recent spike without it scrolling out of view.
Time range opens a submenu of presets: 1, 2, 5 (default), 10, 15, 30, 45, and 60 minutes. The chosen value is the visible width of the time axis.
A longer time range needs more buffered samples and uses more memory; the program keeps history for at least the maximum selected time range.
Auto-scale lets the value axis adjust to whatever the data covers, with a margin above the maximum. Turning auto-scale off freezes the axis at its current min and max so a brief spike does not rescale everything. Toggle this when you want to compare the size of changes rather than the exact values.
The Grid submenu toggles the grid lines:
Defaults: both on.
The Axis labels submenu toggles the axis names:
Defaults: both on.
Both default to on.
The Legend submenu controls what the per-series label shows:
Tick combinations to taste; turning Minimum, Maximum, and Average all on gives a compact statistical summary alongside the live value.
Tooltip lets you pick what hovering the chart shows:
The tooltip is anchored to the mouse position; the time it reports is the time at the cursor.