In the object tree on the left in the Output node, you can find the entry
called Plots. Selecting this will bring you to the plot definition overview
which will probably be empty.
If you click on the "Add default plot"
button at
the bottom, a default plot that contains the concentrations of all metabolites
against the time will be created. To edit this plot definition, double click on
the entry.
"Run"
button again.
Now you a new plot window like the one below, with the concentrations of all metabolites on the y axis plotted against the time on the x axis, should pop up.