Plots can be created inside a worksheet via "Add new" in the context menu or in the application menu via "Worksheet" by selecting "xy-plot" and the type of plot you like to have.
Within this xy-plot you can add a xy-curve containing data to show (again via the context menu or application menu).
The settings of a plot can be changed in the corresponding dock widget. There are general settings like geometry but also the range of the x- and y-axis (including scaling). The plot title can be set in the "Title" tab of the dock widget. Background and border styles can be changed in the "Plot Area" tab.